Plot hole: At the concert in Crowley Corners, Miley announces that she will sing a new song she just wrote, "The Climb." Somehow the band and the backup singers all know the words and the music.
Plot hole: Property is destroyed, museum windows are crashed through, a giant octopus splashes about in the National Mall's reflecting pool, and even the statue of Honest Abe at the Lincoln Memorial comes alive. With all this occurring, not a single D.C. resident seems to notice and nary a single police officer turns up to investigate the goings-on.
Plot hole: After the dinosaur kids wrecked the playground, Manny tells Sid, "Whatever they are, take them back" and someone says "What are they?" as well. Later, when Mummy Dinosaur appears, Ellie says, "I thought those guys were extinct!" and one minute later Manny says, "She's a dinosaur!" How could they possibly not see that the kids were dinosaurs if they already knew about dinosaurs in the first place?
Suggested correction: They weren't sure about the baby dinosaurs' species because dinosaurs were thought to be extinct. The mother dinosaur eventually showing up, with her more convincing dinosaur properties of being much larger and menacing-looking, convinces them otherwise.
Plot hole: From day one, you have to have insurance to even be able to set foot (skate) on the rink. You must provide your drivers license and sign a waiver. Minors have to have paperwork filled out by their parent/guardian. Bliss would have had to show ID to prove her age (she could have a fake, but people can spot those). She would have been busted her first day.
Plot hole: Mr. Cranston asks Denise to be the accompanist for the school's production of "Chicago". This is an error. In the year 2009, in which the film is set, this would be impossible since the licensing company which has the theatrical rights for "Chicago" restricts the show from being produced (even by amateur groups and schools) anywhere in the greater New York area while there is an open-ended production running on Broadway.
Plot hole: In the first film, the shape of the ring was a little different and it was set in a ring. Also, it was given to Xania. In the second film, she was never even acknowledged as donating it to the museum.
Plot hole: According to the phone book the name given was "M. Horowitz" but when Mary mails he first letter to him she already knows it's "Max."
Suggested correction: This mistake is not wrong however wouldn't you think they would have night guards in each of the museums, but no guard is ever seen anywhere.
Creating a silly, Deus Ex Machina solutions for obvious plotholes never resolves them. There is absolutely no way that these things would remain unnoticed by anyone. This entry is correct. This is indeed a plothole because it's much too confusing to be explained.