Residuals have been a standard part of the SAG contract since 1960. Some actors have opted for, and have enough clout to get, a percentage of ownership in exchange for a lower acting fee but the residuals and schedule of residuals is fixed. A producer gets residuals on a schedule similar to actors and other talent (voice overs, musicians, etc) so Schwatrz would get a residual based on being the producer and he would get one as creator of the show. Likely the rights to the show is owned by a production company and likely that in turn is owned by one of the big studios like Sony and possibly some of the rights belong to the original distributor.
Just as an addendum each title someones name appears under in the credits is a separate check and separate residual. So if someone is listed as a producer and an actor they get two checks and two residual checks but also have to belong to both unions.
