It's a giraffe
I heard this joke in a British movie:
Man walks into a bar with a giraffe. They each get pissed. The giraffe falls over. The man goes to leave and the barman says ''Oi! You can't leave that lying there.'' He says ''No, it's not a lion. It's a giraffe''.
I understand that "lying" and "lion" sound alike, but perhaps there's more to it? Does it necessarily have to be a giraffe? Would be the joke less funny if it was, say, a rhinoceros instead?