This is an achievement guide for the Inside Joke achievement in South Park: The Stick of Truth. This achievement is worth 15 gamerscore and is awarded for summoning Mr. Slave while inside Mr. Slave.
This is a missable achievement! Make sure you do Mr. Slave’s side-quest Mr Slave’s Package before you venture into Clyde’s Fortress in the Beat Up Clyde quest.
Upon completion of Mr. Slave’s Package, you will obtain the Mr. Slave summon.
Note that you may only use the Mr. Slave summon once per day. Make sure you save your summon on day 3 for the achievement. Day 3 starts with the Defeat the Underpants Gnomes quest.
During the Beat Up Clyde quest, you will venture into Mr. Slave. While in a battle inside him, just make sure to use the Mr. Slave summon and the achievement will be yours.
Here is an excellent video guide, which will walk you through the achievement as well as the Mr. Slave’s Package side-quest.
Thanks to HappyThumbsGaming for the video!