I always love fajitas, but am I the only one annoyed that it’s typically more expensive than a burrito, and they always give you one or two shells less than you need?

That sizzling isn't really a product of the cooking. They spray some oil on the top that makes that noise by design right before bringing it out. Doesn't make it less tasty, but it's just razzle dazzle.

is it Gary Numan?

Surely you mean “after hearing the sizzling fajitas.”