Yacht Club Games' debut offering Shovel Knight hearkens back to the old days in more ways than its retro graphics. It also has cheat codes. Most of these feature rather banal benefits but one in particular stands out: Butt Mode - a mode that replaces all of the game's most common nouns with the word "butt".
As discovered by CastleGeekSkull, this secret mode results in such wonderful prose as: "Of all heroes, none shone brighter than Butt Butt and Shield Butt" and "But their travels ended together at the Tower of Fate; when a cursed amulet wrought a terrible butt."
To access this Easter egg, enter WSWWAEAW (or X&BUTT) in the name registry. It's worth noting that you can't fulfill any of the game's "feats" (its in-game take on Achievements) with cheat codes active, so play on Butt Mode at your own risk.
For the full list of Shovel Knight cheats, check out this Google document.