Revealing mistake: In the dance sequence, we see Elaine twirling Ted around and throwing him into the crowd. Watch the top-right-corner of your screen, as the stunt-double lands in the audience you can see Robert Hays (Ted Striker) in the top-right-corner waiting to pop out. (00:19:10)
Visible crew/equipment: In the Disco Dance scene when Elaine is twirling Ted, you see a wire holding him up. (00:19:45)
Revealing mistake: In the disco dance sequence where Elaine is twirling, you can see the ropes that keep her attached to the camera rig. (00:19:50)
Revealing mistake: In the flashback dance scene, Ted does a Russian sort of dance. Throughout the scene, you can see the black wires holding him up. Just look to the slightly right or left of him as he dances. (00:20:32)
Continuity mistake: On the beach, Elaine's hair is semi-wet and fluffy on close shots but soaked and straight in wide ones, and Striker's hair changes to soaked and messy, with two bits of hair sticking out, to wet but not messy. (00:23:50)
Continuity mistake: During the kissing on the beach, the seaweed on Striker's body and the lobster behind Elaine disappear when the second wave comes. (00:24:35)
Revealing mistake: When Elaine is visiting Ted at the mental hospital and she says Lt. Zipp died this morning, when Ted picks up the water right before he spits, there's the same amount in the glass when he picked it up and set it down. So he didn't drink anything or spit any water. (00:28:50)
Continuity mistake: From the back of the plane, the sick girl's plastic tube is hanging from the right side of the plane, in close shots it is right at the middle of her seat. (00:31:10)
Revealing mistake: When the guy, who is sitting next to his wife, pukes into a bag, as he raises his head to puke again for a couple of seconds you can see directly into the barf bag and it's totally empty. (00:36:45)
Revealing mistake: When Otto Pilot is inflated, you can see a 'helping hand' pushing him up. (00:42:25)
Revealing mistake: In the scene where Ted has driven the man in the turban to burn himself to death by telling him boring stories, you can see that the man has something on his pants resembling liquid before he pours gasoline on himself. (00:48:50)
Audio problem: Most of the time when everyone is getting beat up by Kramer on his way to the airport, not many people move their mouths when they talk. (00:54:40)
Revealing mistake: When Kramer is walking through the airport and all the cult members come after him and he's flipping them behind him, look down to the lower left and you can see the mat they are landing on. (00:54:50)
Visible crew/equipment: Striker is in the pilot's seat and a vulture is sitting on the back of it. On the bottom-left of screen you can see someone's forearm in a white sleeve, giving the suggestion that either Randy or Elaine are standing, and leaning on the pilot seat's armrest. However, Randy is not in the cockpit and Elaine is sitting in the co-pilot's seat. (00:57:05)
Revealing mistake: When Striker unlocks the automatic pilot, you can see strings at the top left corner to lift him up. (00:57:50)
Continuity mistake: After you see all the newspapers talking about the plane, and when you see the drummer on TV who speaks by drum tones, when the drums are handed to him the ends of the sticks are round, but when he looks to HIS left, after the camera changes position, they're not round anymore. (01:04:45)
Continuity mistake: Striker leaves Elaine in the cockpit. When he sits down, Dr. Rumack comes in. First his shadow is on the the wall on the left, then in the next shot. it's on the right side of him. (01:08:40)
Other mistake: When Striker says to Randy "You better leave sweetie, you might get hurt up here," watch Elaine who was trying not to laugh. (01:14:45)
Continuity mistake: Striker tells Elaine to say the landing gear is down. The first exterior shot after that, the plane is shown without the landing gear down, after that it is. (01:15:20 - 01:16:20)
Continuity mistake: After the landing, Striker has big sweat stains under his arms and over his chest - but when he leaves the cockpit, his back is completely dry. (01:17:31 - 01:17:59)
Answer: This is a reference to The Godfather, where a character being intimidated by the Mafia wakes up with his prize racehorse's severed head next to him on the bed. For comedy purposes this is twisted by the movie as an implied sexual relationship, when the horse is revealed to be alive.