Continuity mistake: When Roger is in the bathroom with Constance (a female alien is disguise) his shirt is unbuttoned but closed almost tight on his chest. Cut to a wide shot and his shirt is wide open, completely bare chested.
Continuity mistake: When Luke is searching through Roger's belongings, looking for any alien "remains" from his encounter, he lifts up Roger's mattress revealing porn magazines. In the next shot the magazines are all differently positioned and much more spread out than in the first shot.
Continuity mistake: As Luke and Alex arrive at the party, Melody comes walking down the hall towards them. In the front shot of her, Melody is walking with her hands at her sides. Cut to a rear view and she has her right hand up by her face, playing with her hair.
Continuity mistake: Right at the end, as Alex and Luke are about to have sex, Alex takes her hair out of her ponytail style and lets it hang down loosely. Her hair is extremely 'poofy' at this time, sort of messy as well. The camera angle changes to Luke for two seconds, then back to Alex. Suddenly, her hair is combed down and straight now...with no 'poofyness' and no hair out of place.