The Big Bang Theory has lined up another interesting cameo.

Following the news that Sheldon's hero, Leonard Nimoy, will be lending his voice to an upcoming episode, TV Guide Canada now reports that this beloved main character will also soon have a "run-in" with Stephen Hawking.

Not much else is known about the appearance of this theoretical physicist, except that it will take place on the show's 21st episode of the season and is the reference at the center of Bill Prady recent Tweets, in which the producer teased a “super-secret, super-cool guest star."

The Big Bang Theory returns with a new episode of Thursday, March 29.