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!
But really, it just looks 
like he put on his goggles.
Pero en realidad, sólo se pone las gafas.
Mas na verdade parece só 
que ele pôs os óculos.