Complexity analysis deals with asymptotic cases where N gets arbitrarily large. Sleepsort would take the same wall time to sort [1,2] and [1,2,1,2] - but it would presumably take somewhat longer to sort an array of 1e10 ones and twos, because it's not a constant time algorithm.

I mean don't get me wrong - sleepsort is intrinsically an extremely funny concept, and I think everyone here gets that. But "constant time" has a rigorous (and pedantic) definition, which sleepsort doesn't meet, so I think for some readers calling it that kills the joke (in the same sort of way that it would kill the joke if TFA's code snippets used lots of invalid syntax).