"Everybody's got their feet on the ground, so it doesn't feel that much different than day one," star Simon Helberg, 33, tells PEOPLE in its new issue, on newsstands Friday.
What began as a series about four lovable brainiacs and the women who love them has blown up into the most popular sitcom on television today, but the show's stars, along with Helberg – Johnny Galecki, 39; Jim Parsons, 41; Kaley Cuoco, 28; Kunal Nayyar, 33; Mayim Bialik, 38; and Melissa Rauch, 34 – say they aim to stay as normal as possible.
"You learn who to talk to, where to go and how to act," says Cuoco, adding that she has developed a simple strategy of her own: "If you don't want to be photographed, don't go to The Ivy, and wear undergarments when you go out!"
By and large, the stars say they much prefer takeout food and each other's company, anyway.
"A lot of us hang out. It's just a close-knit group," says Rauch, who frequently spends time with Parsons and his partner, Todd Spiewak, and Helberg and his wife, Jocelyn Towne. "Kaley is the best at throwing parties. Mayim's the deep thinker, and Kunal is a big giggler. We all get along, and it's a nice family feel."
For interviews with every single star of the show and much more on their loves, lives and bond, pick up the new issue of PEOPLE, on newsstands Friday