Audio problem: During the "Hula Hana" scene, you can tell the little girl with the ukelele is only mimicking playing. A chord is heard being played in a staccato fashion, but the girl is merely rubbing her thumb against the body, and maybe striking the lowest string, while not fretting any of the strings with her left hand. Playing staccato on open strings would require you to use one of your hands to stop the open strings from ringing.
Continuity mistake: In the last dance scene, Patrick Swayze jumps down from the stage and starts dancing. He goes down on his knees and when he lifts one knee, it is extremely dusty, however when he stands up his knees are completely clean. (01:33:00)
Continuity mistake: In the last dance scene of the movie, Patrick Swayze jumps down from the stage and the hair on his forehead which was completely dry is suddenly very wet and plastered to his head. (01:32:30)
Audio problem: When Penny and Johnny are teaching Baby their dance routine, Penny puts on a record. Look closely and you can see that Penny moves the arm to place it on the record, then she takes it away, even though the music is still playing. Even if it's a directorial device for us to hear different music than they do, it's still a mistake because she's not actually playing the record, meaning there isn't any music for them to dance to. (00:36:35)
Continuity mistake: When Baby's family drive into Kellerman's you can see the back of the mum's head, and her hair is blonde. In the rest of the movie she has red hair. This is because the original actress cast as her mother changed after filming had already begun. (00:02:55)
Visible crew/equipment: After Johnny and Baby do their dance at the end of the movie they walk over and Baby's dad stops them. You can see their marks where they are supposed to stand. (01:34:35)
Continuity mistake: When Max is talking with Tito at the end during the final show they're both talking and standing next to the record player. In the next scene they're both standing way off stage (no longer next to the record player) and then Max enters on stage and Tito walks up behind him. (01:27:25 - 01:28:25)
Other mistake: In the scene were Patrick breaks the car window, when he walks to his seat you can see a point of red light (like a laser) on his back. (00:40:45)
Continuity mistake: When Baby and her Dad are on the porch, having a serious conversation about the money for the dancer's abortion, the Dad's collar on his jacket is turned up, then down, then up again. (01:19:35)
Continuity mistake: In the scene were Johnny is fighting Robbie, his belt breaks, and is hanging down. Next shot it is fastened again. And then it is hanging down again. (01:11:45)
Continuity mistake: In the scene where Patrick has just given his speech about how wonderful 'Baby' is, he finishes, walks to the side of the stage, puts down the mike stand and takes off his jacket. In the very next shot, he puts down the mike stand and takes off his jacket again. (01:30:10)
Revealing mistake: After Johnny leaves, they show Baby standing on the porch of her family's cabin. If you look in the background you see two people waiting for their cue before they start walking. (01:24:30)
Continuity mistake: When Johnny has realized that he locked his keys in the car, he takes the pole and breaks one of the car windows with it. The hole he made was about the size of a fist. In the next scene however, the hole in the window is twice as big as it was before. (00:40:35)
Visible crew/equipment: Right at the beginning of the film, 'Baby' is having a group dance lesson with Penny. On the wide shot with Penny wearing a red dress and showing the dance steps you can visibly see a sound boom at the top of the screen. [Fixed in Collector's Edition.] (00:05:40)
Continuity mistake: During the last dance scene, there is a shot of Baby and Johnny dancing on the floor. If you look behind them you will see people climbing up the left side of the stage to start dancing. The shot widens and they are walking on the stage again. (01:34:00)
Revealing mistake: Knee pads are visible on Johnny during the dance at the end.
Continuity mistake: In the scenes where Johnny and Baby have to break into the car, when Johnny looks in to find his keys, it's raining, when he turns to grab the post to break the window, the sun is up and the ground is dry, then when he turns back to actually break the window, it's raining again.
Factual error: In the scene when Baby is changing her clothes in the back of Johnny's car the lights and shadows in the car are moving in the wrong direction. (00:49:30)
Continuity mistake: In the last dance scene, notice the part before the performance, where everything goes dark and the spotlight shines on Baby. You'll see Johnny take off his coat. Then the camera goes back to Johnny offstage taking off his coat again.
Factual error: After the part where they were at breakfast and discussing the idea of leaving early, you can overhear the radio and the announcer says, "Oh, those Mets! What a team! Finally broke their 22 game losing streak!" The longest losing streak for the New York Mets is currently only 17 games, which was in 1962, a year before the setting of the movie. (01:00:33)
Answer: It would be improper to cause a scene, plus Robbie admitted to getting Penny pregnant and insulting her, especially it's what made get an abortion and medical complications.