Plot hole: When Ward's son hits the switch marked "Do Not Touch This Switch", every light in the amusement park comes on, music starts playing, and the rides all start moving. It's a funny gag, but it seems unlikely that one switch would power every single thing in the amusement park, and that everything in the park has been left on "full speed." If that's the case, when Angelo first sent the two lookouts to the top of the ferris wheel, everything else in the park should have come on then too.
Plot hole: Though there's supposed to be a championship football game taking place near the end of the movie, the stadium is strangely devoid of fans. A meager effort was made to fill some seats, but most of the shots show empty ones. It also looks as if the production crew tried to save money by using only half the stadium lights.
Plot hole: Mr. Elliott calls his office in Cleveland, Ohio from the secret pay phone in the lobby, but gets no answer. His wife explains it's 4 AM in Cleveland and that's why nobody answered. However, the island is somewhat close to Hawaii and the time difference is 6 hours during summer. The local time on the island would be around 10 PM. Outside however, the sun is shining. Not possible at 10 PM in that region.
Plot hole: How did Professor Krassman get shocked into being a frog? The electronic device doesn't even touch his head.