"The Pen" is the 20th episode of, the third episode of the third season. It aired on October 2, 1991. This is the only episode in which George does not appear, and one of only two episodes in which Kramer does not appear. This is also the first appearance of Morty's rival Jack Klompus and of Uncle Leo's wife (and Jerry's aunt) Stella.
Jerry and Elaine go to Florida to visit Jerry's parents for the weekend and plan on going scuba diving. Morty Seinfeld, Jerry's father, is also being honored at a ceremony the next night. Jack Klompus comes over to write Morty a check for a previous night's dinner and Jerry notices Jack's pen. When Jerry asks Jack about it, Jack tells him that it can write upside down and that astronauts use it in space. Jack offers an interested Jerry the pen. Jerry refuses his offer several times, but Jack persists and Jerry finally gives in. Helen Seinfeld, Jerry's mother, asks why he took the pen and says he should give it back because Doris Klompus will tell everyone in the condo that Jerry made Jack give it to him.
Elaine sleeps on a sofa bed with a bar that sticks up through the mattress and hurts her back. She is extremely uncomfortable and it is not helped by the fact that the air conditioning is turned off. Jerry tries to console her by saying they only have two more days left before they go back to New York. The next morning, Elaine's back is so hurt that she cannot go scuba diving with Jerry. Morty suggests she take muscle relaxants. Rumors begin to spread around the community that Jerry wanted Jack to give him the pen. Jerry goes scuba diving without Elaine. When he returns, he has black eyes because the capillaries around his eyes burst when he went underwater and pressure was too tight on his mask.
Jack comes over again and Jerry returns the pen. Morty yells at Jack for "taking Jerry's pen". Elaine decides she wants to take the muscle relaxants, but takes a slight overdose and acts goofily at the ceremony. Jerry has to wear sunglasses because of his black eyes. Jack is the Master of Ceremonies and turns the dinner into a "Roast", making cracks about Morty at the podium. Morty starts arguing with Jack again about taking back the pen and they start fighting. The next day, a chiropractor looks at Elaine's back and tells her she should not go anywhere for at least five days, extending both her and Jerry's stay even longer.