Late-1993, renowned astronomer Carl Sagan learnt that Apple's forthcoming computer, the Power Macintosh 7100, had been given a codename of "Carl Sagan" — the joke being that they would sell "billions and billions." This was mentioned in a MacWEEK article some time later, to which Sagan sent the following letter in response.
Apple soon changed the codename to "BHA." Upon learning that it stood for "Butt-Head Astronomer," Sagan filed a lawsuit for defamation of character, and lost. He then sued Apple again, for the original codename, and lost again. So he appealed. Late-1995, the two parties settled out of court, and Apple apologised for any unintended distress caused by the situation.
The 7100's final codename was "LAW." It stood for "Lawyers Are Wimps."
Oh yeah, there's a letter, too. Link -via @shaunusher
(Image credit: All About Apple)