"The Simpsons" has run into music rights issues before, but the only time they've had to change a gag because of it was in episode 3F06 "Mother Simpson". Originally, the song that Smithers taped over Burns' copy of Wagner's "Ride of the Valkyries" with was "Wake Me Up Before You Go-Go" by Wham!, but they wanted something like $150,000 for it. In the final version of the episode, it ended up being changed to "Waterloo" by ABBA, which was much cheaper.
