From SmashWiki, the Super Smash Bros. wiki
The Sheriff universe (シェリフ, Sheriff) is a universe that is represented in Super Smash Bros. 4 by the Sheriff assist trophy. The franchise consists of two games, Sheriff and a simplified remake named Sheriff 2, both developed by Nintendo for arcades in 1979.
The titular Sheriff appears as a trophy.
Sheriff is the first universe in the series to be represented in one installment, have no representation whatsoever in the next installment, and then get some representation again in the very next installment.