Charlie and Dee are very close. They’ve allied one another on several occasions. They have been shown to be naturally more open with each other when the other members of the gang are not around. (as they don’t get peer pressure from the group to make everything a joke) Even though their personalities are fairly different, they have been known to bond really well as they both get outcasted by the gang often. Their friendship began based on who they know in common. Charlie was childhood best friends with Mac, and now is best friends with Dee's fraternal twin Dennis.
- Charlie and Dee knew each other (at least by proxy of Mac and Dennis) in high school, as they were both generally outcast by the general high school populace as well as Mac and Dennis (Dee had her back brace and was called the "Aluminum Monster" whereas Charlie was generally only used as a source of entertainment and forced to eat bizarre and unsafe things in front of bullies, known then as "Dirt Grub").
- In the episode "Charlie Has Cancer" out of all the gang, Dee seems to be the only one concerned.
- In the episode "The Gang Finds a Dead Guy", Charlie goes with Dee to visit her Pop-Pop in exchange for lunch and one use of her car. Dee is very nervous around old people and clings to Charlie inside of the senior living facility where Pop-Pop is housed.
- In the episode "Charlie Wants an Abortion", Dee goes with Charlie and the child whom he has been tricked into believing is his son to the mall and into a toy store. In the store, they spot the Waitress and Dee convinces Charlie to go speak to her. Charlie attempts to have Dee pretend to be his girlfriend, and she refuses. He tries to hug her afterward and she pushes him away.
- In the episode "Underage Drinking: A National Concern", Charlie and Dee are both asked to prom by high school students. On the way home from a high school house party, Dee is seen wearing Charlie's signature green army jacket.
- In the episode Hundred Dollar Baby, both Charlie and Dee train to be competitive fighters. Dee begins taking steroids and Charlie steals them from her behind her back. At the end of the episode, both of them experiencing roid rage, they begin to beat each other up in the street. When Dee pushes Charlie into the hood of a man's car, the man jumps out and says "Listen lady, if you wanna beat up on your little boyfriend, do it somewhere else!" at which point Charlie and Dee chase the man and (presumably) beat him to a pulp, landing them both in jail.
- In The Gang Gets Held Hostage, Dee and Charlie team up in order to survive. They also share a kiss when Charlie says "I love you" in the heat of the moment that is never mentioned again.
- In The Aluminum Monster vs. Fatty Magoo, Dee takes Charlie shopping as he only has four articles of clothing that are all dirty but refuses to help him shoplift anything. When Dee decides to make a dress to get a one-up on her high school best friend Ingrid Nelson. Charlie agrees to help sew it, but later declines after being brainwashed by Mac and Frank in their sweatshop scheme. He also implies that he would like to have sex with her after getting too flustered by Dennis' own dress design sketches which feature only huge breasts and tiny waists. During the scene, Charlie is describing the way he would end up having sex with this woman, then promptly turns and gives Dee a once over before asking, "What are you doing, cause you're looking pretty -- " and then she cuts him off.
- In The Gang Sells Out, Dee helps Charlie get a job at 'Oldies Rock Cafe' but Charlie betrays her and gets her fired for misconduct in an attempt to get closer to The Waitress.
- In Frank Sets Sweet Dee on Fire, Charlie does not seem to care that Dee was set on fire and is more annoyed that she failed to look heroic while saving the cats causing his movie to be ruined.
- In The Gang Gets Whacked (Part 2), Charlie and Dee team up to sell their cocaine and get themselves and Rickety Cricket addicted. They also fail to sell the drugs or to make any money and in the end try to pass off self-raising flour as cocaine.
- In The Gang Dances Their Asses Off Dee and Charlie are briefly paired up as partners and unlike other members of the Gang she does not use this opportunity to drop him. However she later convinces him to get Mac thrown out of the competition and tricks him into eating a brownie filled with cold medicine.
- In Mac and Dennis: Manhunters, Charlie and Dee steal some of Franks meat and have a date like setting with flowers and only one plate, and later learn it might have been human meat causing them to develop an insatiable cannibalistic hunger.
- In America's Next Top Paddy's Billboard Model Contest, Charlie and Dee team up to make viral videos of her "improv" characters. Charlie spices them up by throwing a volleyball at her face in the middle of the shoot and dressing up as Greenman during her shoots. While filming, they are interrupted by a man who recognizes her as PatheticGirl43, a YouTube channel Charlie started with Dee's private video journals. When Dee finds out she has amassed 80,000 hits she tries to milk the channel but once again tries too hard to be funny and appears aloof.
- In Mac and Dennis Break Up, Charlie tries to help Dee get a cat out of her apartment wall by letting more cats into the wall.
- In The Gang Gets a New Member and Dee Reynolds: Shaping America's Youth, Dee and Charlie get jobs at a high school, Charlie as janitor and Dee as substitute theater teacher. Throughout the episode, Charlie constantly refers to Dee as his "best friend" and says that them being best friends inspired him to work as a school janitor. They are fired when Dee brings her class to the bar to watch Lethal Weapon 5 and a student shows up to school in blackface.
- In Charlie Kelly: King of the Rats, Dee takes Charlie to the movies in order to keep him out of the bar while planning his birthday party and appear more altruistic. Charlie doesn't seem to understand the concept of 3D movies and at one point leaps across the seats to shield Dee from something he believed was flying out of the screen right at her. Charlie spills his spaghetti in Dee's purse and frustrates Dee so much that he leaves the theater and she goes to the spa alone.
- In Thunder Gun Express, Charlie leads Dee through the sewers to get to the cinema in time. Charlie tries to convince her to get naked in the sewers for "non-sexual" reasons, which she refuses. Charlie ditches Dee when her shoe gets stuck in the grate and the "wall of water" (raw sewage) washes over her.
- In Charlie and Dee Find Love, Dee is driving Charlie around to help him stalk the Waitress when they get into a car accident. The other car's passengers turn out to be a rich brother and sister who decide to go on a double date with them. Charlie and Dee go on the date pretending to be much higher class than they are but Charlie cracks at the sight of cheese. The brother and sister are relieved to find out that they are lower class.
- In Charlie Rules the World, Charlie and Dee team up to play an online avatar game called "TechPocalypse". Their in game characters briefly rule together. Also when Dee asks Charlie to accept her request to have sex with him in the game he accepts and suggests hopefully if they should do it in real life. When Dee thinks that Charlie's character cheats on her she tries to get him back by sleeping with Mac's character. When Charlie discovers that Dee "cheated" on him with Mac, he goes absolutely ballistic (even to the point of yelling at Frank to "shut the hell up", visibly shocking everyone in the room).
- In Mac and Dennis Buy a Timeshare, Dee enlists Charlie to help her with her pyramid scheme, and they both try to scam Ben the Soldier with The Maniac following close behind. They create a promotional video for the Invigaron berry product, pretending to be rich. Charlie also pretends to be a magical bean farmer named Andy, owner of his own mountain.
- In The Gang Misses the Boat, Mac, Dennis, and Frank storm out of the bar, leaving Charlie and Dee go to a diner and support each other in doing what they want without fear of the rest of the gang making fun of them. Later at Dee's apartment, they get into def poetry together (much to the frustration of Dennis). When Charlie suggests they perform, the two of them make out and it is strongly implied (as well as confirmed by cast members) that something happened. The next day at the bar, they are being very awkward and agree with Frank that the gang should go back to normal.
- In Frank Retires, Charlie and Dee take a blood oath, and agree to remain in cahoots with each other. Charlie also expresses pity towards Dee due to her mother constantly saying "worst is first".
- Season One
- Dee asks Charlie to come with her to visit her grandfather at the nursing home. Charlie tags along after watering down their agreement to him borrowing her car once and a free lunch. Before splitting off onto his own adventure of uncovering her Grandfather's past. (The Gang Finds A Dead Guy)
- Season Two
- Charlie and Dee under the influence of "roid rage" step out from the bar to fight. After a brief but vocal back and forth, Dee pushes Charlie into a parked car. The angered driver steps out of the car and aggressively confronts the pair, which results in their focus being shifted onto the driver. Later on Dennis informs Mac, after getting off the phone with Charlie, that Charlie is in jail with Dee for 'beating the shit out of some guy in front of the bar'. (Hundred Dollar Baby)
- Charlie gets Dee to help him manipulate both Dennis and the Waitress in exchange for Dee being excused from doing Charlie Work. Both Charlie and Dee convince Dennis to attempt to sleep with Mac's mom, and then Charlie's mom, to get back at Mac for sleeping with Dennis' mom. Dee manipulates the Waitress and follows Dennis to convince her that Dennis is a pervert with the ultimate goal of getting the Waitress to sleep with Charlie. (Mac Bangs Dennis' Mom)
- Season Four
- Charlie and Dee team up to find the source of Frank's meat. Eventually deciding that Frank must be tricking them, and that the meat is actually human meat. They bring a homeless guy back to Charlie's apartment, where they attempt to eat him before scaring him off. (Mac and Dennis: Manhunters)
- Season Five
- Team up to try and get the lawyer to perform free legal services for them. (Paddy's Pub: Home of the Original Kitten Mittens)