Version 1:

Fuck, Fuck, Fuck a duck
Screw a kangaroo,
Lick the puss of a platypus,
It's an orgy at the zoo!

(Note: "platypus" can be substituted with "walrus" or "octopus")

Version 2:

Fuck, Fuck, Fuck a duck
Screw a Kangaroo
Gang-bang an orangutan
An orgy at the zoo