What does "slutty" mean here? Does it mean the drink has rum in it?
Great question. Penny is using a play on words because Sheldon ordered a "virgin" drink. A "virgin" drink usually means a version of the drink with no alcohol in it. The word "virgin" is also used to mean someone who has not had sex. Meanwhile, slutty is used to describe someone sexually promiscuous. So she is saying the drinks, which were supposed to not have alcohol, did. It's important to note that this is a play on words in this clip and not a common phrase.