Dream Aliens

They live inside Morty's recurring nightmare, a trio of crude, mocking aliens who taunt him with an exaggerated, garbled voice and repeat the phrase "we're aliens" like a threat and a joke at once. Morty can't wake up or escape them, and they seem to delight in that fact.

They're a small piece of dream logic pushed to its funniest extreme: Justin Roiland's own droning, half-mocking cadence turns a throwaway nightmare into something uncannily funny, because the aliens aren't scary so much as insufferable, taunting Morty with nonsense that somehow still feels like real menace.