Continuity mistake: When they finally arrive at the bottom of the sewer, Eddie's bandage is on a different cheek. (01:59:00)
Continuity mistake: When the Losers Club is in the sewers, the bandage on Eddie's face is on the wrong side in one shot.
Continuity mistake: After they find the club house Beverly tells Ben how handy he is. A bang of her hair is falling on her forehead. In the immediate next wide angle the forehead is clean.
Continuity mistake: Mike's bandage is on the right arm instead of the left (and as previously mentioned, in the same scene, Eddie's bandage is on the right cheek instead of the left). (01:59:59)
Continuity mistake: When the Losers are in the Library, after killing Bowers. They call Bill who is at the funfair. It is night and dark at the funfair, but at the library, daylight can be seen through the window.
Continuity mistake: The mug in the antique shop keeps turning around between shots. Check the painted symbol on it.
Answer: I think it's more of an attempt at a silly joke, juxtaposing the insane imagery with a tender song. But I've also seen the suggestion that it was an Easter Egg/reference to the book "The Langoliers," in which the song is mentioned. (And given the "It" films have some general Stephen King Easter Eggs referencing things from his other books, that makes sense).
TedStixon