Character mistake: In the scene where Steve and Josie prepare to leave to fight the giant robot at the beginning of the movie, Steve tells Will "Oh, Will, a reminder: a lot of the kids at Sky High will only have one super hero parent, not two." When he says "one super hero parent", he holds up two fingers. When he says "not two", he holds up only one finger.
Character mistake: When Casey is using her knowledge of physics to advise a figure skater, she states, "Pull your arms in real tight. That increases your moment of inertia". In fact, this is the exact opposite of how it really works. Reducing her overall radius makes her rotational inertia smaller. (00:21:05)
Character mistake: After the Lieutenant is shot and is in hospital, his CO is explaining what the GHOST system is. He explains that the acronym is "Guided High Altitude Scrambling Transmitter" - which would be GHAST. Replacing "altitude" for "orbit", which is probably what was intended, would make a Guided High Orbit Scrambling Transmitter - or the GHOST system henceforth referred to in the film. (00:06:25)
Character mistake: In the beginning when Karsh and Ileana take the twins Karsh says he'll take Apolla and Ileana says she will take Aretmis but Karsh has the twin with the moon amulet which is Alex, who is supposed to be Artemis and Ileana has the twin who has the sun amulet which is Camryn, who is supposed to be Apolla. (00:00:50)
Character mistake: When Holly and Amber go to see Amber's uncle at the Bistro, they say the 'report' is due tomorrow. However that day will be Sunday (no school!), as previously it was mentioned that the day was Saturday.