The Big Bang Theory has another spin-off under production at HBO Max, titled Stuart Fails to Save the Universe. The show will follow Stuart, the comic book store owner and an unofficial member of the gang. Since the show and some of the characters who will be reprised from TBBT have been announced, fans have been wondering about all the other characters who could make an appearance on the new spin-off.
In a recent conversation with ScreenRant, Simon Helberg, who played Howard on TBBT, addressed the rumors regarding his appearance on the spin-off. When questioned if there were any plans regarding his character, Howard, to appear on Stuart Fails to Save the Universe, he dispelled all rumors and said there was no such plan. Here's what he said and what it could mean for the spin-off.
Howard is not returning for Stuart Fails to Save the Universe

Simon Helberg, who plays Howard Wolowitz, in a recent conversation, revealed that there were no plans for his return to the spin-off:
"There's no plan for Howard to come back at the moment."
Howard Wolowitz, the small, narcissistic Jewish man, started out as the most problematic member of the group (despite Sheldon being a part of that list), but he had an incredible journey of growth throughout the twelve seasons of The Big Bang Theory. He went from a narcissistic, cocky, and quite frankly disgusting man to a romantic, loyal husband and a caring father of two.
So, for Howard's character to return in the Stuart Fails to Save the Universe spin-off would mean disturbing a gift that has been very neatly wrapped up with a bow. Therefore, even if it is sad that we won't get to witness Wolowitz and his smirky sarcasm again, this decision is in the best interest of both Howard's character and the spin-off's future.

Chuck Lorre has been very clear about his efforts to ensure that Stuart Fails to Save the Universe stands apart from The Big Bang Theory, and that too in more than just the characters being reprised. The show is set after the events of The Big Bang Theory, where:
"Comic book store owner Stuart Bloom is tasked with restoring reality after he breaks a device built by Sheldon and Leonard, accidentally bringing about a multiverse Armageddon. Stuart is aided in this quest by his girlfriend Denise, geologist friend Bert, and quantum physicist/all-around pain in the ass Barry Kripke. Along the way, they meet alternate-universe versions of characters we've come to know and love from The Big Bang Theory. As the title implies, things don't go well."
The spin-off is designed to be radically different from The Big Bang Theory, with elements such as CGI that are far apart. It is designed to be something, as creator Chuck Lorre explains:
"I wanted to do something radical that would take me out of my comfort zone. Something the characters on The Big Bang Theory would have loved, hated, and argued about."
Therefore, the only way to ensure that the spin-off, Stuart Fails to Save the Universe, is able to survive on its own is to actually separate it from the original and not bring in the OG gang (maybe a little peek in as a guest star here or there wouldn't hurt anybody).
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