Big Bang Theory spinoff Stuart Fails to Save the Universe featured a surprise fight between a live-action Flash and Mr. Freeze, but the show’s creators originally wanted a different DC hero cameo.

Fans of the sci-fi comedy offshoot may have been surprised to see it dive headfirst into comic book crossover territory when Season 1 Episode 9 premiered earlier this week. The episode saw Stuart Bloom and his universe-traveling companions plopped into a Gotham City come to life, with things quickly taking a turn when none other than classic Batman villain Mr. Freeze (played here by Eric Allan Kramer) shows up.

TV show budgets aside, this is a full-on live-action take on Victor Fries that shoots killer icicles, builds giant ice walls, and even tries to kill Stuart with a giant icy bowling ball. DC fans found even more to recognize when a live-action version of Jay Garrick’s Flash (played by Andy Ridings) ran in to save the day – and deliver a few one-liners.

The Flash has officially appeared in live action in ‘The Big Bang Theory’ Stuart spinoff show. pic.twitter.com/UnfelkJErE

— DCU Brief (@DCUBrief) September 18, 2026

Stuart Fails to Save the Universe packed in the references, with there even being a mention that Golden Age Flash should probably be fighting someone like Captain Cold instead of Mr. Freeze. It was enough to get tongues wagging on social media, with fans mostly just happy to see any live-action Flash for the first time since Ezra Miller played Barry Allen in 2023’s universe-ending standalone film.

“Why is the costume good???” one fan said.

“The clash of the bulky mechanic Mr. Freeze and the vibrant spandex on Flash? Oh yeah, that’s what it’s all about,” another said.

As much of a splash as The Flash vs. Mr. Freeze made, this specific matchup wasn’t the original plan. Stuart Fails to Save the Universe co-creator Zak Penn told Deadline that the episode’s title, “Spoiler: We Couldn’t Get Green Lantern,” was more than just a gag. You can probably guess why Hal Jordan or John Stewart didn’t show up.

“They told us we couldn’t have him because of [HBO’s live-action series] Lanterns, which I understood,” Penn said. “Chuck [Lorre] was a little grumbly about it, but Bill and I pointed out to him that Flash was actually perfect. If we needed something that’s going from dimension to dimension, Flash worked even better than Green Lantern.”

Lanterns, of course, is very much still on the air, so bringing any of its characters – and even potentially its actors – could have been pretty confusing. The DCU show has so far received praise for its grounded approach to two classic Green Lanterns, and it’s clear the Big Bang Theory spinoff was going for something a little more tongue-in-cheek.

#flash #stuartfailstheuniverse homage pic.twitter.com/Yz5e1t6n3o

— Alex Ross (@thealexrossart) September 18, 2026

Stuart Fails to Save the Universe is also in the midst of its first season, which will conclude when episode 10 premieres next week. The DCU is currently without a live-action Flash or Mr. Freeze, but Lanterns will continue to construct its Hal and John when its next episode arrives tomorrow, September 20, 2026.

Image courtesy of Andy Ridings.

Michael Cripe

Freelance Writer

Michael Cripe is a freelance writer with IGN. He’s best known for his work at sites like The Pitch, The Escapist, and OnlySP. Be sure to give him a follow on Bluesky (@mikecripe.bsky.social) and Twitter (@MikeCripe).