Spoiler
Doing my rewatch and found in the episode, the 4 guys are competing in the Physics Bowl. When they kick Sheldon out of the team, they discuss needing a 4th person to complete their team. Raj suggests “that one girl from TVs ‘Blossom’ who is supposed to be really smart”
That actress is Mayim Bialik, who later comes into the series as Amy Farrah Fowler, Sheldon’s future wife.