A weekend that includes 2 or more sleepovers, such as Friday-Saturday and Saturday-Sunday.
Basically, one does not go home after a sleepover, but stays as a guest at another's house for
the night, or goes to a third party's house. It's rather strange and crazier things happen than the normal 2-day events, thusly deserving the "wtf."
It could even take place on days that aren't part of
the weekend (Monday-Thursday)