This art covers, season 6 episode 1 - season 6 episode 18, in a nutshell.

If you have seen these episodes yet, you might be extremely clueless.

The episode was called 28 Pranks Later, a parody name of the movie 28 Days Later. Yes, they were zombies.

Don't want to spoil this episode for you though, so that's all I'm going to say.