And if you must watch any season, watch Season 3 as it's them at their peak. (S2 is good, S1 fun but less clear voice as it uses a few Monty Python tricks, and S4 sadly their patchiest as they had guest stars forced on them.)

....if only to watch Fry regularly hitting Laurie. No, not acting, several times they cock it up and Fry actually hits him!!!!