Penny: Sing Soft Kitty to me.
Sheldon: Soft Kitty is for when you’re sick. You're not sick.
Penny: Injured and drugged is a kind of sick.
Sheldon: [sings] Soft kitty, warm kitty, little ball of fur…
Penny: Wait, wait. Let's sing it as a round. I'll start. [sings] Soft kitty, warm kitty, little ball of fur… See that's where you come in. I'll start over. [sings] Soft kitty, warm kitty, little ball of fur… I've got all night, Sheldon. Soft kitty, warm kitty…
Both: [sing] ...little ball of fur, happy kitty, sleepy kitty, purr, purr, purr.