Stuart Bloom (Kevin Sussman) may have killed Howard's (Simon Helberg) mom, Mrs. Debbie Wolowitz (voiced by Carol Ann Susi) in The Big Bang Theory, at least according to one hypothesis. It's been more than two years since the CBS sitcom wrapped up after 12 seasons. However, The Big Bang Theory remains as popular as ever thanks to reruns, not to mention its availability on various streaming services around the world. Given this, viewers have been revisiting the show and picking up information that may have slipped them the first time they watched it.
Premiering in 2007, The Big Bang Theory revolved around a group of geniuses who were also dubbed as social outcasts. Their lives changed upon meeting Penny (Kaley Cuoco) — an aspiring actress who moved to Hollywood to pursue her passion. By season 4, the cast expanded with the introduction of Amy (Mayim Bialik) and Bernie (Melissa Rauch) who eventually married Sheldon (Jim Parsons) and Howard. Since then, the sitcom had become a mixed narrative of their personal and professional lives. The latter involved their respective families who factored in either individual or multi-episode narratives, including Mrs. Wolowitz - despite never appearing fully on screen.
In The Big Bang Theory season 7 finale, it's revealed that the comic book shop owner moved into the Wolowitzes after his business suffered a fire. During this time, he became the official caretaker of Mrs. Wolowitz who needed a full-time keeper given her injury. The pair became good friends, and so in spite of Debbie's recovery, Stuart continued to stay at her house. Later on, it was revealed that Mrs. Wolowitz gave Stuart the money needed to reopen the comic book store. Reddit user u/Joblezz posits that chances are that this was a loan that was never put on paper. So when she died, that essentially meant free cash for him. Given this benefit, it's not outside the realm of possibility that Stuart gradually killed Mrs. Wolowitz, which wouldn't be that difficult considering that she was already suffering from a lot of health problems.
To further back this theory up, the source added that when Howard's mother left for her last trip, Stuart took the liberty of taking the furniture from her den. He claimed that Debbie allowed her to take them, but it's a big coincidence that Howard could no longer confirm this with his mom because she died thereafter. Assuming that Stuart did plan out Mrs. Wolowitz's demise, the timing of the re-opening of the comic book store was also perfect. That meant that he no longer needed to keep her as leverage against Howard, who was getting increasingly suspicious that he was mooching off of his mother. Looking back, this thesis has merit since Stuart has had a lot of chances to execute his scheme without anyone finding out. Howard Wolowitz was mostly out as he lived separately with Bernie, while Mrs. Wolowitz, for some reason, was enamored by him.
Admittedly, it's a pretty dark idea for a sitcom like The Big Bang Theory - but also one that does have some credibility behind it. The timing of events line up, and Stuart has the motivation to do the crime. At this point, there's no way to know if this can be accepted as canon. Nevertheless, it's an interesting notion to ponder on.