Originally, Freddie Mercury was supposed to be at the pool party, but Queen said no. They did, however, allow an appearance by John Deacon, which worked out as Deacon was the one who wrote "Another One Bites the Dust", which is not mentioned in the scene but Deacon's insistence on that song being parodied by Al puts more emphasis on the satirical portrayal of Deacon as a self-centered semi-celebrity.
Daniel Radcliffe actually learned to play the accordion for the film. He first took lessons from a friend, then 'Weird Al' Yankovic himself while on set. He admits to not playing very well, but passable enough for the movie.
When looking at the flyers for band auditions, one flyer is advertising "Kuni's Karate School". Kuni was a character from 'Weird Al' Yankovic's TV Pirada (1989) who ran a karate school and berated his pupils for being "stupid".
Inspired by Weird: The Al Yankovic Story (2010), a "Funny or Die" short starring Aaron Paul as Al and Patton Oswalt as Dr. Demento. 'Weird Al' Yankovic himself appears in the short playing a similar character to the one he would play in the full-length film.
Daniel Radcliffe was chosen by 'Weird Al' Yankovic partially as a result of seeing him sing The Elements on The Graham Norton Show (2007). The performance had stuck in his head and when they started casting, Radcliffe was his first choice. The 5.5" Radcliffe being much shorter than the 6 foot Yankovic also added to the humor.