Jonathan Coulton has publicly shamed Fox for plagiarizing his arrangement for "Baby's Got Back" on its TV show "Glee":
Writing on Techdirt, Mike Masnick has a good, nuanced view of how this kind of thing works:
Yes, his is a cover song, but he introduced some variations that appear to be directly copied in Glee. Is there a potential copyright claim here? Well, that depends -- and the copyright law here is complex. You can cover a song by paying compulsory license fees, and Fox likely did that to whoever holds the copyright on the original. But they copied specific changes (and possibly the music) that Coulton added, which, could potentially be covered by his own copyright (of course, whether or not he registered them could also impact what he could do about it). And, let's not even get into the issue of things like sync licenses for video, and the (still open) question of whether or not Glee actually used part of Coulton's own recording.
In the end, though, almost none of that probably matters. Because Coulton seems unlikely (we hope) to go legal here. Instead, he's just going with the public shame route -- with a simple tweet about the situation, which has set off "the internet" to help him make his case and embarrass Fox and Glee.