When someone tends to frequently and suddenly leave with little to no warning, based on Snufkin from The Moomins, a vagabond that tended to disappear for up to half a year.
Person 1: Hey, this party is pretty good right 2?
Person 2: It's minnow season *leaves*
Person 1: wtf
Person 3: Don't worry about it, they just have a Snufkin Complex