The flashback indicates the Angry Dad webtoon was released in 1999. Jimmy Fallon--the show Homer was supposed to badmouth the Angry Dad movie on--started airing in 2009. Since Bart is only ten, this would be impossible.
The song playing in the background of the 1999 flashback is the studio version of "Bye Bye Bye" by *NSYNC which was released in early 2000.