Long before they starred on The Big Bang Theory together, Mayim Bialik and Johnny Galecki shared their first-ever onscreen kiss on Blossom.

When the cast of the CBS comedy appeared on Conan on Wednesday, the duo was confronted about their epic makeout, with co-star Kunal Nayyar demanding Bialik and Galecki "do it again." While the pair declined at first, they later relented with a long, sloppy kiss that got the entire crowd cheering.