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!
That's why the goggles were removed 
from the beginning of the anime!
¡Es por eso que las gafas fueron removidas desde el principio del anime!
Por isso retiraram os óculos 
do começo do anime!