It sounds like complete bullcrap, but if you look closely enough at the word's entry in the Oxford English Dictionary, you'll find the first plural form listed is in fact "beeves." Same goes for Dictionary.com and Merriam Webster. According to Google Books, "beeves" saw the height of its popularity back in the early 1800s, before trailing off by the 20th century. It has, however, recently seen a small resurgence since about 1995 — presumably because that was the year AOL first made useless trivia like this easily available to the masses via the world wide web. Or, you know, the incorrect form was starting to be some people's pet beeves. (Thanks Chris.)