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 Sket Dan is a school club that 
does odd jobs with three members:
El Sket Dan es un club de escuela que hace cualquier trabajo con 3 miembros:
O Sket Dan é um clube de colégio 
que faz de tudo com três integrante: