Allow me to take you back in time to October 1st 1992 when Cartoon Network began it's life; introduced by Droopy Dog the first of Cartoon Network's presenters, we were then treated to Cartoon Networks first broadcast cartoon Bugs Bunny in "Rhapsody Rabbit"

Bugs Bunny is one of the cartoon old guards as this particular cartoon was made in November 1946 in which Bugs Bunny plays Hungarian Rhapsody No.2 at a concert but is constantly interrupted and later upstaged by a mouse, and if that concept sounds familiar then you may have seen Tom & Jerry's "The Cat Concerto" released six months later in April 1947 which won a short film Academy Award (This is back when Cartoons did win Oscars)
This is where this Urban Legend began.
During the era both cartoons were submitted for the short film entry by their respective companies Warner Bros & Metro-Goldwyn Mayer, the plots of both cartoons were the same, both featured the same music and both released round the same time. Both companies accused each other of plagiarism and even accused Color Motion Picture company Technicolor of staging the plagiarism in the first place by sending prints of the cartoons to both rival companies.
In the end, "The Cat Concerto" won the Academy Award while "Rhapsody Rabbit" didn't even get a nomination, 45 years later "Rhapsody Rabbit" earned a title that no one can take away from it as first aired Cartoon Network Cartoon.
To this day the issue has never been resolved with many believing the situation to be coincidental but others point fingers at Tom & Jerry as being the guilty party as their cartoon was rushed to make that years nominations and the fact that Bugs Bunny's cartoon was copyrighted first.
Either way it doesn't change history and gives more work to cartoon historians.
(I so want to do that as a career)