Continuity mistake: When Buddy's dad opens the present from Buddy, he holds it directly above the box. In the next shot, a closer shot, he is holding it next to the box. The following shot shows him holding the present directly above the box again.
Other mistake: When Buddy confronts the department store Santa (Artie Lange), watch the kid sitting on his lap. He's mouthing the words of both Buddy and Santa as they're saying them.
Continuity mistake: When Buddy is in the Lincoln tunnel, the busses alongside him change positions between clips.
Other mistake: When Buddy's brother gets a skateboard from Santa Claus in Central Park the skateboard trucks are mounted incorrectly. Both are mounted the same direction. The kingpin always faces the inside of the board, but here one is mounted facing outside.
Continuity mistake: When Buddy is drinking the Coke, the bottle turns to show the label.
Answer: This was a real event. The Simon and Garfunkel free concert drew a crowd of over half a million people and the Central Park Rangers were investigated for being a little "over-enthusiastic" in their methods of crowd control. It was 1981 though, not 1985 as stated.
Absolutely correct and thank you - I was there at the concert and it was 1981. I love the movie Elf but that incorrect reference is a slight irritant - LOL.