The Waitress slept with Dennis after he told her Charlie had cancer. Charlie told Dennis he had cancer as an elaborate ruse to get Dennis to convince the Waitress to go out with Charlie out of pity. After sleeping with Dennis, he and Mac offer her 250 dollars to sleep with Charlie. She and Charlie go out on a date but do not sleep together. Mac and Dennis demand their money back but she refuses. ("Charlie Has Cancer")
After Dennis and Dee's recent addiction to crack cocaine they are demoted to doing "Charlie Work" at the bar and Charlie is made manager. To get out of doing Charlie work Dennis goes out on a date with the Waitress and threatens to sleep with her if Charlie doesn't call his phone and tell him he doesn't have to do Charlie work any more. Charlie then uses Dee to manipulate the Waitress into thinking Dennis was having sex with Mac's mom and Charlie's mom as part of a plan to convince her to get back at Dennis by sleeping with Charlie. To get back at Dennis the Waitress instead decides to sleep with Dennis's father Frank (also Charlie's roommate) whose toupee falls off her during sex ("Mac Bangs Dennis' Mom"). Charlie is visibly upset as he begins to tear up.
The Waitress who is a recovering alcoholic offers to be Charlie's sponsor in AA as part of a misguided ploy to get Dennis to fall for her. Dennis uses this as an excuse not to interfere with whatever relationship Charlie and the Waitress might have going on. The Waitress refuses to sponsor Charlie any more so he gets drunk and ruins the basketball game of the kids the Gang are mentoring for community service. ("The Gang Gives Back")
Dennis and Dee stalked the waitress when they were pretending to be serial killers. The Waitress maced them. ("Mac Is a Serial Killer")
Dee, Charlie and Dennis manipulate the Waitress into giving them jobs at the restaurant she works at. Dennis flirted with the Waitress to get the job but he pays her back by getting the phone numbers of the hot girl customers at the restaurant and drinking on the job. Charlie calls the franchise owner who fires Dee, Charlie and Dennis. He also fires the Waitress for being dumb enough to hire them. The Waitress needed a second job because a Starbucks had moved near the coffee shop she works at for her other job and was siphoning customers away. ("The Gang Sells Out")
The Waitress promises to sleep with Mac in exchange for helping her get the sex tape Dennis recorded of them having sex for his collection. It is revealed that Dennis filled it under W for Waitress as he still does not know her real name. Mac wants to sleep with the Waitress to get back at Charlie for supposedly destroying his Project Badass video. In actuality Charlie loved the Project Badass video and was destroying the sex tape of the Waitress and Frank. The Waitress suggests that Mac bangs her in Charlie's apartment to further the insult. However, her real motive for this is to destroy the sex tape Frank made of the two of them when the Waitress slept with Frank to get back at Dennis in Mac's Banging Dennis' Mom. ("Mac's Banging the Waitress")
After hanging out with Dee and Artemis the Waitress falls off the wagon and begins drinking again. She tells Charlie that is she going to go out and bang the first guy she sees. Charlie asks if it can be him and the Waitress says no but it could be Dennis which Dennis overhears but is clearly not interested. ("Who Pooped the Bed?")
Frank tricks the Waitress into coming to Dennis and Dee's inaugural podcast by telling her Dennis is going to apologize to her. The twins laugh at her and mock her instead. Frank offers to pay her 500 dollars if she takes her top off and drinks soup out of Frank's shoe. The Waitress, always desperate for money agreed with the shoe part but refused to take off her top. Rickety Cricket says they don't have soup and dumps a bucket of dirty mop water on her instead thus further humiliating her. ("Mac's Big Break")