South Park: The Stick of Truth - Dragon Wrath Achievement

Achievement - Dragon Wrath
Hit 3 enemies with a single fart outside of combat.
**This is a Missable Achievement **

You must use a single fart to knock out three enemies at once, not just hit three enemies with your fart. The best time to get this achievement is during your second visit to the school. By this time you will have learned the Sneaky Squeaker, which lets you lure enemies to a specific spot. There are at least 3 parts in the school during your second visit where you can lure 3 enemies together and then use the environment to knock them all out.
You can use Clyde's castle as a last-ditch effort.