The Behemoth have a novel and pretty sweet unlock system for new characters in recently released BattleBlock Theater. If you finish one of two (solo or co-op) Furbottom's Features levels (player created) you unlock a new character, however, this promotion is limited to two weeks. Currently, you will unlock "Toast", previously characters like Winston, Donuts and Furbottom have been made available, but fear not - even if these characters won't be around for a while - at some point they will be made available again.