Who appears as Dr. Greg Pemberton in season 12?

Sean Astin appears as Dr. Greg Pemberton in season 12 of The Big Bang Theory.

Astin plays Pemberton in “The Plagiarism Schism,” the twenty-first episode of the final season. Pemberton is one of the physicists whose work accidentally confirms the super-asymmetry theory developed by Sheldon Cooper and Amy Farrah Fowler.

The story places Pemberton and his colleague Dr. Kevin Campbell in competition with Sheldon and Amy for recognition connected to the Nobel Prize in Physics. The rivalry becomes ethically complicated when Barry Kripke uncovers evidence that Pemberton plagiarized his doctoral thesis. Sheldon and Amy must decide whether exposing the misconduct is justified, even though it could improve their own chances.

Astin is especially recognizable from The Goonies, where he played Mikey Walsh, and from The Lord of the Rings, where he played Samwise Gamgee. On The Big Bang Theory, however, he plays a fictional scientist rather than himself. His appearance is therefore easy to remember as both a casting surprise and a plot-critical guest role.