Other mistake: In the party scene, the monster chews repeatedly on a blonde man in a white tuxedo while suspiciously humping a table. This happens while Slade locks the car. There's another shot of the partygoers running away scared, but that is recycled from the earlier bit when the alligator tail-whipped a security guard earlier; the guests that are running away are the exact same (look for instance at the woman with the brown dress and the black belt). You can even spot the security guard flying again in the air like a minute earlier. (01:16:25)
Other mistake: Henry Silva is interviewed by a reporter played by Sue Lyon in her last movie appearance. She holds a microphone with the familiar peacock symbol of NBC on it, but in the end credits she is "ABC Reporter." (00:50:10 - 01:25:45)
Other mistake: When Henry Silva is trapped in the jaws of the animal and screams asking for help from his indigenous sidekick, the beast is hardly crushing his body, more like holding it in place with no damage to his clothes or blood, and then turns it around between shots. (01:06:00)
Other mistake: The alligator baits Col. Brock through a feat of chinese shadow puppetry certainly quite unlikely for the intelligence shown in the rest of the movie, and inconsistent with the movements he's capable of, not to mention the fact that he would have needed to perfectly abscond covering himself in trash bags super-fast, flawlessly, silently. (01:05:00)
Other mistake: David is trying to locate the beast through a map of the city - for some reason, since he already located it before. Problem is, the movie is set in Missouri but the map he's looking at on his bed is a map of Los Angeles (you can even read "Granada Hills"). Similar mistake a few minutes later in front of the sewers; you can easily read "Monterey Park" to the right of a different map he props against the wall. (00:37:15 - 00:38:35)
