- "I think it's kind of cool! I mean, when I met you guys, all you did was stand around and talk. But now you can't walk five feet without getting wrapped up in some crazy adventure."
- —Doc's speech to the Blood Gulch Crew in Reckless
Doc has developed multiple relationships since he first appeared, but despite having many positive relationships with several characters, Doc is commonly abused by the main cast. Because the Reds and Blues didn't notice his disappearance during Season 12 and never searched for him, Doc redeveloped his "O'Malley" pysche and was resentful to the group. However, after the group apologize and ask for his aid in Counseling, Doc accepts and forgives them because all he ever wanted was to be appreciated by the Blood Gulch Crew.
Doc's relationship with the Reds vary from being friendly or annoying. After the Blood Gulch Chronicles, Doc spent more time with the Reds than the Blues.
Although Doc treats Sarge decently, Sarge seems to dislike Doc, seeing him as annoying. This is possibly because Doc crashed into Sarge twice with the warthog. When Sarge returns to Valhalla, as soon as he hears Doc, he tells Simmons to get his gun and commence 'Operation: Point-My-Gun-At-Doc'. In Season 11, Sarge seems to treat Doc better, although Doc is annoyed by Sarge trying to convince him that he has a "natural lust for murder."
When Doc disappeared during the Chorus Trilogy, Sarge never noticed his absence and even believed that Doc was always with them until he was "rescued" in Season 13. Although Doc is reunited with the group, Sarge seems the least aware of his presence, as in The Thin Fed Line, Sarge is the only one in the Blood Gulch Crew who doesn't realize that Doc could help the relationships between the Chorus armies when he runs by them.
Simmons and Doc seem to be friendly to one another. Both have similar traits and are very intelligent. Simmons stated that he was sorry for getting Doc involved in the situation with Meta and Washington, suggesting that Simmons does care for him at some level. However, when Doc gets stuck in the wall, Simmons abandons him when the Meta attacks, although Simmons does attempt to free him first.
Doc is shown to be happy upon seeing Simmons and Sarge in Three's a Crowd. In Reckless, Doc states that Simmons got his old team back, which touches Simmons. Despite this, Simmons is shocked and soon enraged when Donut only brings Doc and Lopez to rescue them in Season 11. After Doc vanished due to Grif throwing a Teleportation Grenade at him in Ready…Aim…, Simmons barely noticed his absence, explaining to Tucker that "[Doc] just got one of those faces, you know? Like really forgettable," after finding Doc in Temple of the Key.
Because almost no one noticed his disappearance, Doc redevelops his "O'Malley" psyche and fierce anger, which is why Simmons originally was disappointed that Doc would survive his wounds in Off - Key. However, when Simmons realizes that Doc could help improve the Rebels and Feds relationship because he was literally neutral, Simmons later begs with the rest of the Blood Gulch Crew for Doc's aid and he accepts, restoring some of their relationship.
When Doc is taken captive by the Reds, he and Grif were able to get along. However, when Doc learns Grif isn't liked very much, Doc abandons him. Ironically, when Doc was abandoned by both teams, Grif cites the same reasons for abandoning him, and since then their interactions have been minimal and somewhat hostile. In Season 11 however, the two are shown getting along much better, with Doc even willing to help Grif test the future cubes and hang out with him while they searched the ship.
When Grif accidentally teleported Doc away when they were preparing for the battle of Crash Site Bravo, which led to Doc's disappearance, he shows no concern and even forgets about what happened to Doc until he was "rescued" in Season 13. After the Blood Gulch Crew beg Doc to help them once they return to Armonia, Doc gives an example with Grif how a role-playing session can help mend Kimball's and Doyle's relationship, but Doc goes into his O'Malley personality and insults Grif and his family during the example, saddening Grif. Because of this and the fact Grif is responsible for his disappearance, it's implied that Doc now despises Grif (knowingly or not).
Originally, when Donut learned of Doc/O'Malley's plan, he was afraid of them and called him the "cave devil". However, after the events of Revelation, the two became friends after Doc saved Donut's life and the two lived together in Valhalla. After Don't Say It, Donut returned to Valhalla to continue living with Doc before the two went to "rescue" the other Reds and Blues. It's also implied the two are now best friends, as Donut's Basebook page has an image of him and Doc with the hashtag BFFLS, which is plural for "Best Friends For Life", in Reconciliation.
Despite this, Donut only subconsciously noticed Doc's absence after he was caught in one of Grif's teleportation grenades, as he states it's weird that it "feels like he hasn't seen [Doc] in ages," when "rescuing" him in Dish Best Served. Although Doc redevelops his "O'Malley" psyche and fierce anger because almost no one noticed his disappearance, Donut expresses great joy of his return and explains to Doc what has happened on Chorus since he vanished. Their relationship was somewhat restored when Donut begs with the rest of the Blood Gulch Crew for his aid, which Doc accepts.
After kidnapping Lopez, Lopez becomes both O'Malley and Doc's henchman. However, Doc seems to have friendlier conversations with Lopez than Lopez does with O'Malley, as the two agree more often then O'Malley does with Lopez and Doc got a Gmail invite from him. Although Lopez is angry about Doc forgetting about him in Season 5, he seems to forgive him. Doc and Donut also decide to bring Lopez with them to "rescue" the Reds and Blues. After Doc goes missing toward the end of Season 11, Lopez is the only one to notice, and in Catch Up, No Mustard, Lopez mentions how Grif's actions caused Doc to go missing in the first place.
During the Blood Gulch Chronicles, the Blues saw Doc as annoying because he's a pacifist. However, they seem to treat him better as the series progressed.
Doc and Church seem to get along quite well, to the point where Church considered Doc a teammate. However, Doc crudely corrected him that he was neutral at the Blues' worst time and was against Church when he wanted to kill Junior. Church also was happy for putting Doc in mortal danger by sending him to fix a malfunctioning Sheila.
Doc and Tucker treat each other like acquaintances. Tucker does at one point consider Doc as a perfect baby sitter for Junior, possibly because Doc helped deliver Junior as well as take care of him while Tucker was in a coma. However, Tucker was surprised that Doc was able to get Sister to strip naked for him. During Doc's absence in the Chorus Trilogy after Grif threw a teleportation grenade at him, Tucker never noticed his absence and even thought that he was with the Reds until finding Doc in the Eastern Mountain Range.
When Tucker reveals that the Blood Gulch Crew were never looking for him despite Doc believing his "friends" appreciated him, Doc ultimately snaps and redevelops his "O'Malley" psyche before tackling Tucker and beating him until Grey stops him. Because of this, Tucker is greatly annoyed by Doc's "renewed" personality and their relationship has become strained.
In Motion to Adjourn, Doc rubs Caboose's neck with aloe vera to treat his foot injury. Caboose seems to be afraid of Doc, at one point telling Church not to contact him in Season 4 (though it's likely he was afraid of O'Malley). After Doc fed some of Caboose's blood to Junior, he tells Church "Don't leave me with the horrible doctor," scared of what else Doc may do. However, as the series progressed, Caboose seems to have taken a liking to Doc. Despite this, Caboose did join the others in beating up Donut and Doc after hearing about their "rescue" attempt in Long Live the King.
Caboose barely noticed Doc's disappearance after he vanished in Ready…Aim…, but unlike Tucker, Caboose seems happy about his return in Season 13. He laughs along with Doc when he slips into his O'Malley personality and Caboose remembers his time with Doc fondly when explaining who Doc is to Grey (while Tucker was being beaten) in Dish Best Served. After "rescuing" him, Caboose begs with the rest of the Blood Gulch Crew to help improve the Rebels and Feds relationships and later appreciates how Doc's counseling "helps" his relationship with Tucker in Counseling, restoring their relationship.
While the two don't interact much, Doc was originally sent to Blood Gulch to help Tex but failed, being three months late. Tex is directly responsible for O'Malley infecting Doc, however, as when she killed Omega in Caboose's mind she failed to account for Doc having his radio on. Tex apparently had no qualms about killing Doc as if her plan to kill Omega at Zanzibar succeeded, Doc would've been killed to. Near the end of Revelation, he watches Epsilon-Tex fight the Meta and Washington with Epsilon.
Doc is the first person to learn of Tucker's pregnancy and was able to successfully deliver Junior. Since Junior was born, Doc treats him with great care, teaches him, feeds him, and walks him. Doc was clearly fond of Junior and Junior most likely feels the same. This is shown when he defends Junior, using his rank, when Church wanted to kill the latter. After Tucker awakens from his coma, he considers Doc a perfect baby sitter for Junior.
While the two are never seen interacting Doc presumably helped Flowers after Omega left his mind.
When Doc did a physical exam on Sister in Missed Direction, he was fascinated by her flexibility and told her that her color blindness wouldn't harm her chances on the battlefield. Since then, he has lost interest in her. When they got lost in the caves together, he was tired of her stories and thought she talked too much. Sister, however, shows no negative or notable opinion of Doc. She also convinced him to help Flowers after Omega left his mind.
Doc and Washington seem to hate each other when they first meet, due to the fact that he became Washington's prisoner and Washington was annoyed by him. Doc often tries to chat with Wash and give him suggestions, such as saying that the Freelancers should strike due to not getting paid overtime, but Wash orders him to shut up. Wash mostly shows disrespect towards Doc, refusing to take any logical advice that he suggests. However, Doc still saves Wash's life, and afterward Wash entrusts him with protecting Epsilon, possibly meaning that Washington may now have some respect or trust in him.
Later on, Doc states Wash got what he wanted, which was a new and trusting team. Despite this, Wash, along with the other Reds and Blues, did beat Doc up when he and Donut failed to rescue them in Long Live the King. However, this was out of anger, and throughout the rest of the Chorus Trilogy, Wash shows no ill will towards Doc and accepts him as part of the Blood Gulch Crew.
Doc's relationship with Epsilon seems far better than the one he has with Church, as the latter has been shown to trust Doc. This includes when Doc helped him recover in n+1 and Epsilon asked Doc to use the Epsilon Unit on him, but Doc refused. However, in Season 9, Epsilon refused to call for medical help after he is shot by Donut, believing medics to be bad luck. When Doc is reunited with the Blood Gulch Crew after being "rescued" in Season 13, Epsilon seems happy about his return but shows confusion about Doc's group therapy session in Counseling.
Doc was possessed by Omega for a long period of time. When he was first possessed by O'Malley, Doc was originally scared. However, he became more willing to help in O'Malley's plans and even told him that his head had enough room for the both of them while O'Malley enjoyed Doc's medical practices and preferred him to be his host. Despite his kind actions toward the A.I., O'Malley was generally annoyed by Doc's happy and supportive nature and, being a pacifist, Doc is against O'Malley's plans and ideas for conquest. However, due to Omega, Doc became more aggressive and was willing to stand up for himself.
Despite Omega's destruction in Reconstruction, Doc has redeveloped his "O'Malley" psyche in the Chorus Trilogy due to the long period of time he was once possessed by the A.I. and his most recent mistreatment by his friends. Not only does Doc consider his split personality as if it was Omega himself, but it's shown that his "O'Malley" psyche helps him express his true feelings and allows him to finally overcome his pacifism to fight, as shown in Armonia, Part 1. In conclusion, while Omega's possession over him possibly harmed Doc's psyche overtime, Omega aided Doc far more through developing his confidence, aggression, and skills.
Doc seems annoyed by Vic and hates talking to him, due to his comments and odd behavior. It's also shown when Omega possessed him, he expressed his hatred to the character greatly.
Doc shows fear of the Meta, even more so when the Meta punched him into a wall. However, he still insulted both the ex-Freelancers, such as when he successfully caused the Meta to malfunction, Doc continued to insult him and when he was interrogated, he called the two "Bad cop and even worse cop." He later stated that seeing the Meta eat someone would be interesting. The Meta, on the other hand, simply found Doc annoying and later betrayed him and Wash after the battle at Sidewinder.
After meeting Felix in Neighborhood Watch, Doc treats his injuries for protecting him and the other Blood Gulch soldiers. Although questioning his methods, Felix appreciates his aid and explains everything during his interrogation. However, Doc and the others aim their weapons at Felix during FAQ when they mistake him for a Freelancer, before the latter explains that he's a mercenary. After his return in Season 13, Doc learned from Donut about Felix's betrayal during his absence, making Doc the last member of the Blood Gulch Crew to lose all respect for Felix and see him as an enemy.
When they meet again in The End is Near, Doc aids the Blood Gulch Crew in defeating Felix, clotheslining the mercenary with his Rocket Launcher before firing a rocket at Felix. During so, Doc mocks Felix villainous actions and belief that he's better than them, stating in his O'Malley personality "Oh, please. I'm the original bad boy." Doc, along with the rest of the Reds and Blues, then watch Felix fall to his death.
Doc's first encounter with Emily Grey was not a pleasant one. After Doc had demonstrated his split personality in front of her, Grey quickly became intrigued. She then suggested and prepared electroshock therapy for him. However, Doc, resuming his original personality, was frightened and ran off, encouraging a chase from Grey, during which one of her comments suggested a romantic interest (albeit psychotic).