Continuity mistake: When Alex's Dad arrives home at the end of the film, he hands Alex a remote control car box. Between a wideshot and closeup the box turns around 180° in his Dad's hands. (01:32:10)
Continuity mistake: When the leader of the robbers is looking for the chip he rips the car apart across the street in Mrs. Hess's house. He doesn't find it. About five minutes later the parrot is riding the car into the snow fort and again in the house.
Continuity mistake: A little way into the film, Alex is talking to his mum in bed whilst she is applying lotion to his chickenpox. One moment his shirt is open, the next it is buttoned up and closed, but there was no time for his mum to do it up, it happened in a split second.
Continuity mistake: When Alice does flips to try and get on to the back porch of the house, her hair is different after she turns around to walk towards the door.
Continuity mistake: After Alex calls the police the first time, his mother herds him into his room. When they first enter there is a shot of his bed, the top pillowcase's open end is first facing right. Then there is a close up of Alex and the open end is facing left. It continues switching to the right whenever the shot is from farther away, to the left when it's a close up of Alex.
Continuity mistake: When the FBI are rushing to reach Alex, as the snowploughs sweep the spy's car aside the front plough sweeps to the left. Further down the street the front plough sweeps to the right.
Continuity mistake: At the end, when the parrot is going into the igloo, the igloo looks tiny from the outside, as if Alex would barely fit in there. But when the parrot goes into the igloo, the man can fit in there and there is so much more space in it.
Continuity mistake: Alex's mother goes to make him a sandwich and squeezes jelly onto the bread. The shot comes back after both Alex and his mother talk before she goes out. The jelly has mysteriously been spread.
Continuity mistake: In the very first shot of the Mom, she carries in a load of boxes. Two green ones are included, one with writing above the other. When she unstacks them, the shot pans out a little bit, and the boxes are positioned differently.
Continuity mistake: When Unger gets run over by his criminal partner, look at the driver side window. Making initial contact with the car, it is closed. For the close up shot, it's wide open, and when the car turns, it's only open a couple of inches.
Continuity mistake: Alex's Dad hangs up the steamer in the attic, when Alex informs him that his taxi arrives. The metal holder the steamer hangs on changes position with every shot.
Continuity mistake: When Miss Hess leaves the plane after landing in Chicago, she takes a scarf out of the Parisian bag she has accidentally picked up. Surely she would have noticed the items within the bag were not hers when she put the scarf in the bag?
Continuity mistake: In the scene where Alex's mum is about to leave his room after applying lotion to his chest. Alex's hair is slightly scruffy - when the shot comes back to him after being on the mum his hair is combed and neat.
Continuity mistake: When the luggage goes through the scanner at the start of the movie the bad guys put their toy car on the belt followed by a brown bag. Scene then cuts to the old woman, and she picks up the bag which is the same bag as the bad guys', followed by a blue one. When the bad guy pick their bags up it's still in order they put it on, nothing swapped.
Continuity mistake: When Beaupre and Unger get smashed by the trunk of books, it shows them clearing the books off them. When they are shown again, Beaupre still has a book on his chest.
Continuity mistake: The main bad guy has Alex cornered in Mrs. Hess' garage. Look at the clear plastic cup behind Alex. One shot the cup is upright, the next it is on its side.
Continuity mistake: The scenes where the bad guys get into Chicago are in daylight, but when they are "chasing" the taxi cab it is nighttime.
Continuity mistake: When the police are arriving at the end of the movie (behind the snow ploughs), there is an overhead shot showing sunlight shining onto the street. Every other shot in that exact scene is otherwise grey and cloudy.
Continuity mistake: When Alex runs into the garage towards the end of the movie, we see sunlight shining in through the window. Wasn't it just grey and snowy outside?
Continuity mistake: When Alex first takes out the bubble-squirting gun and threatens Olek Krupa's character with it, the muzzle looks like what one might see on a real gun. However, when we get a closeup of it after Alex shouts at Olek Krupa and chases him away, the muzzle has a gaping hole in it, because it's a different bubble-squirting gun.
Answer: It was Jernigan who thought there was a woman in the shower and he couldn't take the risk that if it was a woman, that she would eventually get out and see intruders in the house and call for the police. The only option open to Jernigan would be to kill her so there'd be no witnesses.
No it was Beaupre who thought there was a woman in the house.
I've seen the movie and I can confirm that it was Jernigan who opened the shower curtain because he thought a woman was in the shower.