As for season 1 mentioned above, I rewatched S1 before S4 and holy hecks I recognized like everyone. Even people that just show up briefly as side characters I know from other shows. I know shows with good budgets will often draw from the same pool of minor stars, but that was something else.
Season 1 was super good, season 2 was good. Never got down to watching the 3rd though, just seen that Chris Rock stars in the 4th! Will get to it eventually.