Here's the trivia behind it:
"The cake SpongeBob got for Patrick says 'Sorry about the scabies'. Scabies is a skin disease in humans where mites burrow into the skin and cause a rash that is similar to mange in animals with fur. In this case, scabies is an an STD to those in Bikini Bottom, like it would be in the human world."
Someone please tell me how in the hell that got past the radar. I'm seriously baffled by this.