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!
Our pride as odd-jobbing Jumpers, 
and our very existence, is on the line!
¡Nuestro orgullo como trabajadores independientes de Jump, y nuestra misma existencia está en juego!
Nosso orgulho como faz tudo da Jump 
e nossa existência estão em jogo!