The Big Bang Theory’s Kunal Nayyar reveals behind-the-scenes secrets

Big Bang Theory favorite Johnny Galecki is clearly a gum-removing machine.

Joining the Sunday Lunch guest lineup alongside Samm Henshaw and Liz Bonnin yesterday (January 30), his former partner Kunal Nayyar (who played Raj in the hit sitcom) revealed revealed a rather crude behind-the-scenes secret about his co-star.

Explaining the logistics of the apartment staircase where Leonard, Sheldon and Penny all live, the actor said: “The way it works is, you go down the stairs and then they yell, ‘Wait.’ . They change the scene from as if the apartment says 1a suddenly it says 2a or 3.

Related: Queer Eye star stars in new movie with The Big Bang Theory’s Jim Parsons

“They changed the scenery to look exactly like another floor.”

Apparently, all the actors will remain in their positions after descending each floor as the costumers work their stealthy magic.

“You run back up the stairs, get nowhere, and then you walk back down as if it were a new floor,” Nayyar added.

But this is where Galecki’s dirty habits come into play.

“There’s nothing down there, there’s a wall where Johnny Galecki, for 12 years, stuck his gum on it.

“I’m not joking,” his co-star promises. “There’s a wall of 3,000 pieces of Johnny Galecki’s dried gum.

“So if any of you are Johnny Galecki fans and want his dried gum, I’m sure it’s for sale somewhere on the internet. Welcome to Hollywood.”

Sunday Lunch airs Sundays on Channel 4. The Big Bang Theory airs on CBS in the US. You can now buy the complete box set on DVD and Blu-ray forms.