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!
The anime began airing in 2011 at the 
same time the new Gintama began airing.
El anime salió al aire en 2011 al mismo tiempo que la nueva temporada de Gintama.
O anime foi ao ar em 2011, na mesma 
época que o novo Gintama foi ao ar.