Denise is the new assistant manager of Stuart's comic book store.
Being into comic books, Denise is intelligent enough to know what kinds of comics certain people like. She is also very good-tempered most of the time.
When the comic book store suddenly starts to become popular, which Sheldon isn't too thrilled about at first, Stuart hires Denise as his new assistant manager. Sheldon isn't crazy about her initially, but starts to warm up to her as he discovers she knows what kinds of comic books he prefers. After hearing all about her from Sheldon, Amy barges into the comic book store and asks Denise for advice on comic books.
As Sheldon and Amy’s wedding approaches, Stuart asks Denise to come to the wedding with him. She is hesitant until she hears that Mark Hamill is going to be at the wedding too. Stuart buys her a dress, and they sit together, and he impresses her by revealing that he knows more about Star Wars than Mark Hamill.
Early on in the twelfth season, Stuart and Denise begin developing a relationship and having sex at the Wolowitz house, which Howard and Bernadette aren't too thrilled about.
Later on, in The Paintball Scattering, Denise begins looking for a new roommate, and selects Stuart to be her roommate, which he is hesitant about. When Denise and Penny are captains for two teams in a paintball game, Penny takes Stuart on her team. During the game, Denise shoots Stuart several times, causing him to accidentally shoot himself while fleeing from her. They ultimately make up with a kiss and Stuart agrees to move in with her.
When the gang goes to Sweden so Sheldon and Amy can win their Nobel Prizes, Stuart and Denise stay behind to babysit Halley and Michael, but eventually find themselves slightly in over their heads, leading to Bernadette's parents taking over.