Access Butt Mode in Shovel Knight by entering "X&BUTT" or "WSWWAEAW" in the name entry screen. As with all cheat codes in Shovel Knight, applying Butt Mode means you won't be able to complete any "feats," the game's achievements.
Yacht Club Games tweeted the cheat code this week, and CastleGeekSkull shows off Butt Mode on YouTube, proving that yes, it is as funny as it sounds. And we are all 6 years old. See that video below.