I'm surprised that some US state (especially the one Springfield is in) didn't come up with this idea first, but WE did. See the world's first official Simpsons number plate at:
http://tinyurl.com/2r5rrh (eBay auction for charity.)
Current bidding is at $55,700 ("Are there ANY serious bids?") but with 8 days to go no doubt they will achieve a reasonable donation.
(Hell, that's 56 times what my *car* is worth!)
Paul