Linux 4.0 Doesn't Have The Weirdest Codename
While Linux 4.0 is codenamed "Hurr durr I'ma sheep", Linux 3.0 was codenamed the Sneaky Weasel while the last of the Linux 2.6 series was codenamed Flesh-Eating Bats with Fangs. Yes, the codenames are generally quite odd with some other codenames being like Sheep on Meth (Linux 2.6.34/2.6.35), Funky Weasel is Jiggy wit it (Linux 2.6.25), and Arr Matey! A Hairy Bilge Rat! (Linux 2.6.23~2.6.24). Going back to the Linux 1.3 was the Greased Weasel codename.
If you have a slow start to the week and want to ponder over old kernel codenames chosen by Torvalds, there's an entire Wikipedia article devoted to Linux kernel names. Or if you wish to be more productive starting off the week, read about the changes coming for Linux 4.0, formerly known as Linux 3.20.