The Big Bang Theory - Episode 1.12

Sheldon seeks players to be part of his team to compete at the Physics Bowl Competition. Amongst those he recruits are the office cafeteria's lunch lady and her son. The episode also features Dimitri, a Russian physicist who now works as a janitor where Sheldon works. It wouldn't be surprising if Dimitri is asked to be on the team as well.

Source: SpoilerFix