E255

e255 is just the shortened name, because Wikia couldn't grasp it's true form, ??.@'?]-?e??255

??.@'?]-?e??255 could be considered an intentional glitch, as the graphics are messed up and contain random characters. It is the encountered when you position a dart monkey, a sniper monkey and boomerang next to each other, all 1,4, on any map. It only appears 55 rounds after the conditions are met, at the end of the round, so it could be considered a late-game boss. It has 100k health and 20 AD. It also has a 50% chance to dodge attacks. They absorb all magical attacks, healing it for the amount of damage it would've done.

Abilities
???-?e??255.?---?]]]]??//????: Deals 0 damage to your monkeys, but actually sets their HP to 1. CD: 1 second

@'????v.?fa-- -0)?? sd: Summons copies of itself, but they have 50 hp and 0 AD, but with the same abilities. CD: 5 seconds

d' 45????`/v??.??c'}: Gulps up your strongest tower, healing it fully. Single use. Uses it at below 1k health.

Trivia
This boss's name and abilities are a direct reference to ??.@'?-?e??255], or more commonly known as The Glitch, from EBF4.