Is this a joke I'm too dense to get or is this just plain bullshit? What I found on Wikipedia was this:
Haggis (Scottish Gaelic: taigeis) is a savoury pudding containing sheep's pluck (heart, liver, and lungs), minced with chopped onion, oatmeal, suet, spices, and salt, mixed with stock, and cooked while traditionally encased in the animal's stomach though now an artificial casing is often used instead.
I don't even think a three-legged mammal exists. However I did find this: (emphasis mine)
Wild haggis (given the humorous taxonomic designation Haggis scoticus) is a fictional creature of Scottish folklore, said to be native to the Scottish Highlands. It is comically claimed to be the source of haggis, a traditional Scottish dish that is in fact made from the innards of sheep.
But obviously that's something different as it's native to Scotland and is just fictional.