Complex sentence: Bopper is ecstatic, and is preparing to cut the Stooges a check, until he overhears the sneaky stooges talking about how the film was a hoax, as they played the cavemen themselves.
Split into simpler sentences: Bopper is ecstatic, and is preparing to cut the Stooges a check. However, Booper overhears the sneaky stooges talking about how the film was a hoax, as they played the cavemen themselves.