This definition would make eating pizza itself a niche thing, topping or otherwise. 33% of the population is mainstream and it isn't an option to claim otherwise. Less popular? Yes. Fringe? No. Fringe is something like Linux on the desktop at sub-1% of the market. It is not feasible to ignore or marginalise 1 person in 3.

I'm certainly impressed by the position that the most popular show is the fringe one. In theory it is possible, but practically that is a hard sell.