A Wallaweeb is a derogatory term for an outsider who obsesses over Australian culture. The name derives from "Wallaby" (a small, Kangaroo-like creature found in Australia) and "Weeb" the shortened version of Weeaboo (an outsider who obsesses over Japanese culture).
"You know, Vegemite is genuinely phenomenal. You just have to develop a pallet for it."
"Steve, quit being a wallaweeb. That crap tastes like spicy toe jam."
This type of person will never hesitate to tell you how much pot he is going to smoke when he gets home, but not before he shits his diaper and parks his car in your living room.