Gennice is an up-and-coming actress serving as Bette Midler’s understudy in “Rochelle Rochelle”. As Jerry starts dating her, he notices she is easily driven to tears at the most minor inconveniences (like dropping a hot dog on the floor). Ultimately, it’s too much for Jerry to take, and the two break up.
Gennice is played by Adelaide Miller, and if that name doesn’t ring any bell, don’t worry about it — other than her “Seinfeld” episode, the actress only has five credits to her name, all of which are pretty minor and date from 1990 to 1996. What happened to her after that is still a mystery.
Laura
One of the several Lauras decorating Jerry's love life is initially introduced as the roommate of another love interest — Sandi. When Jerry purposes all three of them have a... let's call it "adult sleepover" together, he's surprised to find out they are on board, and that the thought of going through it is making him uncomfortable.
Actress Heather Medway plays Laura in that episode ("The Switch", 1995). She has only had one memorable role since — Cameron Westlake in the TV series "Viper", but she quit acting altogether in 1999, two years after having her first child with writer/producer Danny Bilson.
Shelly
In "The Doodle", Jerry and his designated girlfriend Shelly go out on a double date with George and his own designated woman. The incredibly random reason for their breakup is him refusing to use her toothbrush upon finding out he's left his at home, which was being fumigated for fleas.
Dana Wheeler-Nicholson, who plays Shelly, has done a lot since her part on the show. This could be why you're scratching your head trying to understand where you might know her from. If that helps, her latest big roles are Beverly O'Connor on the musical TV show, "Nashville", and Angela Collette on "Friday Night Lights".
Melanie
Jerry has broken up with his many girlfriends over the dumbest reasons you can think of. The one that probably takes the cake, however, is Melanie, who he broke up with because of the way she eats her peas (one at a time).
The pea-eating chick is played by the beautiful Athena Massey, who sadly hasn't landed many bigger roles afterward. She's contributed her voice to video games and had a small recurring role in the TV series "Black Scorpion".
Holly
In "The Wink", Jerry goes on a date with Holly, Elaine's cousin, and soon ends up regretting it. After eating a salad at a steakhouse, Jerry feels like he has to eat more meat around her to prove his manhood to her. She then cooks him some mutton, which he pretends to enjoy right before he spits into her precious napkins. Classic.
Stacey Travis, who plays Holly, went on to have small parts in many hit shows after her Seinfeld appearance, including "JAG", "Mad About You", and "Two and a Half Men". Most recently, she was seen playing the small recurring role of Nikki in the TV series "S.W.A.T.". Thankfully, no further napkins were damaged there.