Gintoki was thrown in prison after being framed, and while he's made an enemy of the warden, he's managed to become the boss of the prisoners.  With his underling Shachi in tow, Gintoki skips his menial labor duties to search the warden's room for anything incriminating.  Understanding that the punishment will be fatal if they are caught, Gintoki disguises himself by putting on pajamas...
Everybody Loves Pajamas
Todo Mundo Adora Pijamas