What does “festa do pijama” mean in Portuguese?

A festa do pijama is a sleepover: children, or adults being silly, staying the night with sleeping bags and no real intention of sleeping. Portuguese builds the name as festa + de + whatever defines it, so it says literally “party of the pyjama.” The same frame gives festa de aniversário (birthday party) and festa de casamento (wedding reception).

The clip is a washing machine full of clothes talking to each other, and the joke turns on that very frame: the party clothes brag a gente é roupa de festa, “we’re party clothes,” and the pyjamas answer foram numa festa? festa do pijama — the only party a pyjama ever attends. Note the gender: it is o pijama, masculine, despite the final -a.