Other mistake: When Chet is getting on everyone's case about everything that is wrong with the house, he says to Lisa, "I didn't think it was a whale's d__k, honey" in reference to the missile going through the house. The French subtitles has "bitte" to mean the portion of the male anatomy. The correct French word is "bite". "Bitte" means either "bite" or "bollard" in English. (01:14:10 - 01:16:10)
Continuity mistake: After the party, when Chet gets out of the vehicle, he has five shotgun shells in the front of his vest. As he walks up the stairs, he has three shotgun shells in his vest. A few seconds he opens his bedroom door and he has five shotgun shells in his vest again. (01:14:45)
Factual error: When Anthony Michael Hall is being pursued by the police, they have the logo of City of Los Angeles, but this takes place in Chicago. (01:18:40)
Continuity mistake: In the scene where Wyatt and Gary are taking Deb and Hilly home in the Ferrari and Porsche, Gary is being pursued by the police. When Gary approaches the railroad tracks, the train is shown coming in the direction of the passenger side door. When they finally cross over the tracks, the shot is flipped, and the train is seen to have crossed the intersection in the direction of the driver's side door. (01:19:25)
Revealing mistake: When Gary is being chased by the police, a stunt double in a blond wig is driving his car. (01:20:35)
Revealing mistake: When Gary and Wyatt come home and see Chet turned into a pile of poo, Chet shoots his tongue from his mouth and catches a fly. Look closely, the tongue flies completely out of his mouth and is attached to a metal spring. (01:24:55)
Continuity mistake: During the storm of Lisa's creation, when Wyatt shouts to hang up the phone, Gary leans over Wyatt's arm and places the handset back onto the phone base. However, after Gary shouts, "What's going on?" the handset is still on the modem.
Continuity mistake: When Gary grabs the FDX system unit (Memotech), the monitor (with green text) which sits atop the system unit falls backwards, and he then throws the system unit out the window. However, the FDX unit is back on the desk, with the monitor atop it (they are between the display monitor and feed scanner), when the boys are on the floor.
Continuity mistake: After Lisa's creation, in the car Wyatt's left hand is resting on the back of Lisa's seat, but when Lisa asks why Gary chose the name Lisa, Wyatt's hand is gone, only to reappear and disappear again depending on the angle of the shot.
Audio problem: At the bar when they're leaving, Anthony Michael Hall's mouth doesn't match up to anything being said.
Revealing mistake: Wyatt's grandmother is supposed to be frozen solid, however she moves a bit when we see them in the closet.
Visible crew/equipment: During the party, Deb and Hilly join Gary and Wyatt in the bathroom, and when the boys step into the shower enclosure and close the glass door, a crewmember's moving reflection is visible on the shower head.
Chosen answer: They probably only had permission to use the song at the cinema and take home releases, so when shown on broadcast TV they'd have to use another song.