As pointed out by Reddit user imbattinson, when Stuart first debuted on "The Big Bang Theory," he was something of a romantic rival to Leonard. He asked Penny out on a date, and it went surprisingly well. Had Sheldon not interrupted their alone time to debate Stuart on who would replace Batman if he died, who knows where things could've gone. Building on this, the episode "The Classified Materials Turbulence" once again saw Stuart and Penny hook up, though she slipped up and referred to him as Leonard during their date. Thus, their fling came to a close, and the rest is history.
Thankfully for the historically unlucky Stuart, his dating life wouldn't totally fall to pieces after Penny. He'd also date Amy for a brief period as well as Howard's second cousin Jeanie (Kara Luiz) before meeting Denise (Lauren Lapkus). Stuart hires her as the assistant manager of his comic book store during Season 11, and the two fall in love soon after. "I was excited to see what was going to happen with that storyline," said Kevin Sussman at the Paris Manga & Sci-Fi Show (via Roster Con), where he admitted his disappointment in not getting to see where Stuart and Denise's lives would go as a couple.
Stuart and Penny were quite the odd couple, so it's fair to say that everything turned out for the best as far as their romantic lives go. It's just too bad that we didn't get to see more out of Stuart and Denise's relationship before "The Big Bang Theory" concluded.
