In the "The Big Bang Theory" episode "The Pancake Batter Anomaly", the ordinarily snippy hypochondriac Sheldon (Jim Parsons) catches a severe cold, unwittingly passed to him from the ever-healthy Penny (Kaley Cuoco). Sheldon's roommates take the opportunity to flee the apartment, and Penny is therefore roped into caring for Sheldon. Penny soon learns how odd Sheldon's illness requests are. For one, he insists she rub Vick's VapoRub on his chest, which she begrudgingly agrees to. As she does, however, Sheldon demands she also sing one of his favorite childhood lullabies, a Polish folk song called "Soft Kitty." He sings it for her, and she attempts to follow along. Penny is immensely annoyed.

The song immediately became beloved by "Bang's" many fans, however, and it would be sung in eight additional episodes of the series, sometimes under very bizarre circumstances. "Soft Kitty" is one of the show's more notable running gags.