Johnny Galecki and Sara Gilbert Together Again

Johnny & Sara in 1992. (Wireimage.com)

Former Roseanne co-stars Johnny Galecki and Sara Gilbert are together again — this time on the new comedy The Big Bang Theory, premiering tonight at 8:30 p.m. on CBS.

On the new sitcom, Johnny plays a nerdy physicist while Sara is slated to guest star in an upcoming episode as a co-worker he attempts to date.

Johnny told OK! at the CBS fall season party that Sara’s newborn daughter, Sawyer, 7 weeks old, is making life interesting on the set. “She cries during rehearsal,” Johnny said, adding a joke: “That’s the only thing I’m not liking about working with [Sara] this time around.”

Johnny and Sara played boyfriend and girlfriend and eventually a married couple on Roseanne, which ran from 1988-97.

The actor said working with Sara again is “immediately familiar, like a day has not passed.”

But time has flown and Sara is now the mother of two with her longtime partner, Alison Adler. The couple also has a son, Levi, who turns 2 next month.

Johnny, on the other hand, has no immediate plans to start a family. “[Sawyer]'s always on the set, and she’s the most beautiful child I’ve ever seen. [But] I’m afraid of handling those tiny little babies. She’s much too fragile for my clumsy hands. I’ll wait five or six years [to have my own kids].”