The stars stopped by Conan on Wednesday along with the rest of the Big Bang Theory cast ahead of the show's 200th episode. And Bialik and Galecki were confronted with their first on-screen kiss with each other in the 90s on the show Blossom.
"It might have been my first real-life kiss, also," Bialik, 40, revealed.
Host Conan O'Brien then dredged up a throwback photo of the scene, showing a young Bialik and Galecki leaning in for a smooch – Simon Helberg couldn't help but take a jab at Galecki's colorful shirt, "I think Rue McClanahan wore that."
Soon, the two locked lips in an intense (and lengthy) smooch with the audience cheering.
The 220th episode of The Big Bang Theory airs Thursday at 8 p.m. ET on CBS.