by Scorpion0x17
I did see one theory put forth by someone that did make some sense:That the Abomination was a late addition to the game, and the 'just a Fatty' symbol was just a Fatty, and the 'Fatty plus' symbol was a Fatty plus two walkers, but then, rather than redo the spawn cards when they added the Abomination, they just made it so that Fatties always come with two walkers, and used the 'Fatty plus' symbol for the Abomination.