Is this a pan-pan or a mayday?

[The Heff]

In theory, it would be Pan-Pan; in reality it was (quoted from BBC website):

Originally Posted by Braden Blennerhassett

You're not going to believe me, and its not a joke, but I have a snake on the plane!"

I've heard of animals making homes in aircraft; such as birds nesting in the cowling, and earwigs hiding in the pitot tube. What other bestial stowaways have been found in the aircraft?