The first season of Seinfeld (1989) wasn’t really a “season” at all, with only five episodes total, including a pilot that bore little resemblance to the series that would follow: The sets were all wrong, Kramer was called “Kessler” (and had a very different personality), and most egregious of all, there was no Lainey! Boo to that!
Curiously, the episodes are presented on the DVD in their production order, rather than their broadcast order, which means that Elaine (Julia Louis-Dreyfus) doesn’t appear until three-quarters of the way through her “first” episode (#1.4, “Male Unbonding”), and we don’t get a fuller explanation of her relationship with Jerry until the following ep (#1.2, “The Stake Out”).* Obviously those early episodes are a little rough around the edges, and far from the quality that viewers came to expect in later years, but it’s clear that the uniquely talented cast were already starting to gel, and find the rhythms and quirks that would stand them in good stead when they got the chance to really strut their stuff.
Aside from Liz Sheridan, who makes her debut in ep #1.2 as Jerry’s ‘Mom’, the most notable supporting actress is Lee Garlington, who appears in the pilot as ‘Claire’, a snarky waitress at the (wrong) coffee shop where Jerry and George go to talk about nothing. According to the casting notes at Wikipedia, there are various theories about why her character was written out… but Garlington has racked up over 200 acting credits to date (including the unnecessary American remakes of The Bridge and The Killing), so her career doesn’t seem to have suffered too badly from the snub…
* Though we do get to see her fend off a pass from a charmless non-friend of Jerry’s, played by Kevin Dunn… who would go on to appear with JLD in several seasons of Veep!