This episode is a sidestory!  Gintama has been involved in many (one-sided) crossovers.  This time, they're working with the Jump comedy manga Sket Dance!  An episodic anime that airs on Thursdays at 6 PM about a group of three odd jobbers with plenty of laughs and tears...  Sounds very similar to Gintama.  As Gintoki warns that the Sket Dan is coming after Gintama, the Sket Dan members appear and offer a challenge!
It can't mean that...
No puede ser eso...
Não pode ser que...