| The South African euphemism that Pseudo_Intellectual relates is far from an isolated case. For some reason, a bizarre amount of euphemisms for sunshowers involve the marriage of animals. An informal 1998 survey* by Bert Vaux, a Harvard linguist turned up around 30 "animal wedding" terms, in languages as diverse as Japanese, Zulu, Arabic, and Finnish. It is quite possible that additional instances of this pattern remain undocumented, "in the wild" of language, as it were.
Other popular expressions, common in many languages, include human marriages, animal births, and the exploits of devils (frequently pictured marrying, traveling, celebrating, or beating their wives). The similarity of all the versions of these expressions suggests an origin in some common proto-language, or somewhere in the collective unconscious.
A list of the animals used in these expressions (and the languages they occur in):
Fox
Monkey
Wolf
Bird
Bear
Donkey
Elephant
Leopard
Lion
Mouse
Jackal
Rat
Siar (a small deer-like animal)
Tiger
*Vaux's complete results are viewable at http://www.emich.edu/~linguist/issues/9/9-1795.html#1 | 
