Key & Peele got it right; two pumps are allowed.
Two weeks after Steelers receiver Antonio Brown drew a flag and a fine for a pelvic-thrust celebration that included three (maybe four) pumps, Broncos receiver Emmanuel Sanders escaped both by stopping short of three.
While it’s possible Sanders added a third pump (CBS cameras cut away after two), the NFL tells PFT that Sanders was not fined.
The two plays had striking similarities. Perhaps the only difference was the number of pumps. Which would indeed make Keegan-Michael Key and Jordan Peele prescient.