The greatest bad movies moments to date!
"Watch for Snakes!"
No, Samuel Jackson didn't deliver this line, nor did it take a horde of internet enthusiasts to write it. While Arch Hall and gang are searching the desert for the titular caveman, Eegah, a male off-screen voice shouts "Watch out for snakes!" followed by a female going "Ooooh!" Both lines are obviously dubbed in post-production, but considering snakes are never referenced again, you have to wonder why. Granted, based on the level of "horror" to be found in Eegah!, the snakes line was probably an honest attempt to ratchet up tension.
Runner Up: Dune Buggy Orgasms
While being toured around on her boyfriend's dune buggy (supposedly in search of her missing father), the female protagonist in Eegah! screams "Yippee!" and "Whee!" more than Anakin Skywalker in a pod racer. Added are various moans and groans of excitement. Remembering that once again this has all been dubbed in after the fact (and goes on for several minutes) one has to wonder just what the hell was really going on in that dune buggy.
"Your Stupid Minds, Stupid! Stupid!"
Plan 9 from Outer Space has so many great bad movie moments it's almost too tough to keep track of. When the very concept of the movie seems like a joke, it's tough to narrow things down. Nevertheless, the film reaches its philosophical and narrative climax when the humans board the alien space vessel and confront the aliens behind Plan 9. The chief alien explains that the human race is about to develop a super weapon called "solarmanite" which explodes sunlight and thus the entire universe. The humans are incredulous to this, and so are admonished by the quoted line.