Simon Helberg, Melissa Rauch

Howard finally returns from space on Thursday's The Big Bang Theory — and if you ask Simon Helberg, he may as well have been in orbit too.

"I was actually isolated, confined to a tiny area, when we were shooting the space station stuff, so it lends itself naturally to that theme," he tells TVGuide.com. "I was separated from the cast, I was shooting on a different day than the cast. It was like I was in space, or on a completely different show. I was lonely and I was nervous that I would incinerate upon entering their atmosphere or something. I mean, talk about an easy way to kill someone off! It's like Suzanne Somers on Three's Company when everything was shot via phone calls on a separate set."

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Unlike Somers and Chrissy Snow, Helberg and Howard Wolowitz are not going anywhere, except back to Earth now that Wolowitz's space mission is complete. But his re-entry doesn't exactly go according to plan — his plan, that is. Expecting a massive hero's welcome, Wolowitz is bummed to return to just his wife Bernadette (Melissa Rauch), who is unfortunately nursing a cold. Everyone else is entrenched in a highly combative Battle of the Sexes game night, and even his overbearing mother is preoccupied — with her new boyfriend and Wolowitz's dentist Dr. Schneider (Ken Lerner).

"Nobody seems to care and everybody's doing other things. ... Howard walks in later [on their game night] and hopes they will roll out the red carpet, and nothing," Helberg says. "Bernadette's the only one at the airport for him, so immediately he's like, 'Oh. My friends are not here. At least I'll be with my wife tonight.' But she's sick and passes out, so then he decides, 'Oh, I'll get some affection from my mother,' which is basically banging your head against the wall. He resorts to seeking out his mother! Then she turns out to be with his dentist! Of all the things he was expecting when he came back, it definitely wasn't a sock on her door."

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The readjustment period is something actual astronauts go through, Helberg learned after discussing it with Mike Massimino, who recurs as himself as a member of Wolowitz's space crew. "People are nice and obviously excited when you get back for a moment, but then it's back to reality," Helberg says. "It's a sort of culture shock. I don't know what the right expression would be. Planet shock, maybe. You've just been looking down on Earth for however long and now you're back, and the same sh-- is going on and you're not a big deal. You're just one of a billion people."

Not that Wolowitz will realize this right away, of course. Instead, he will maintain the astronaut schtick in hopes of fielding public adoration. "He's wearing the NASA shirt every single moment he can. He works in something about space [into conversations] and it's starting to drive people crazy," Helberg says. "But it's a good icebreaker to throw that in. You could only imagine what [a good pickup line] it'd be if he wasn't married!" It's not until Bernadette tells him to cool it in next week's Halloween episode — in which they dress as Smurfs! — that it all comes to a head. "Everyone is tired of hearing about his adventures in space, so it reaches a breaking point at this costume party and it's hilarious."

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Once Wolowitz figuratively comes back down to Earth, he'll have to deal with the most pressing matter at hand: His and Bernadette's living situation. The mama's boy still hasn't worked up the courage to move out, let alone tell his overbearing mother. "He's sort of half in both places at this point," Helberg says. "It's clear to both of them that he technically lives with Bernadette, but he's got enough stuff at his mom's that he hasn't quite cut the cord. It's like the Annie Hall thing: I have my place and the reason I have it is because I know I have it. That starts to create some tension."

But shouldn't knowing your mom is hooking up with her beau next door be enough impetus to move out? "You'd think," Helberg laughs. "You hear enough that it's clear something terrible is happening. I'm warning everyone right now: It's scary."

The Big Bang Theory airs Thursdays at 8/7c on CBS.