The character Jake Jarmel was introduced in 5:4 The Sniffing Accountant as Elaine's boyfriend/upcoming author, although the actor who portrayed him, Marty Rackham, first appeared on Seinfeld, Marty first appeared, as mentioned above, as Officer #1 in 4:2 The Trip Part 2. Marty came back to reprise the role of Jake Jarmel two more times so that audiences can have their fill of JJ.
Jake doesn't realize that when one takes phone messages, one must capture the feelings of each caller; he cooks, so he knows his way around the kitchen, except where the cork opener is, and I can only imagine how he would be with stove repair science, as stove repair instructions does not guarantee stove repair safety; doesn't think it's appropriate to stop for candy when someone gets in an accident, or at least one that is severe enough to be sent to the hospital; doesn't like people having his Malaysian sunglasses; and apparently is a good author who likes signing with Lippman.
JJ's character can be summed up by Kramer's response to JJ, "Well that's peculiar."
(per episode except Cousin Jeffrey, Larry David, Farvman, and Lauren Bowles)
Jake Jarmel = 3
Jake Jarmel (1st Time) - 5:4 The Sniffing Accountant
Jake Jarmel (2nd Time) - 5:22 The Opposite
Guys Who Broke Up With Elaine
Jake Jarmel (1st Time) - Exclamation Marks
Jake Jarmel (Marty Rackham as Officer #1) - 4:2 The Trip Part 2
Jake Jarmel (as Jake) - 5:4 The Sniffing Accountant