When Drax and Mantis encounter the police on earth, Mantis disables and hypnotizes Officer Fitzgibbon into sleeping. She then stands up and fights two more cops coming out of a different squad car, one of which is just Officer Fitzgibbon again.
When the band is performing at the end of the film, the singers are singing into the wrong side of the microphone.
Mantis says to Kevin Bacon that he fought Jason Voorhees. Jason wasn't the killer in Friday the 13th (1980) that Kevin starred in. Jason didn't start killing until Friday the 13th Part 2 (1981).