According to Jim Recap: Geronimo Jim
When Ryan decides that he wants to learn how to drive a stock car, Dana puts her foot down - which has the exact opposite effect, and Ryan wants to do it all the more. So Cheryl explains how it works. She tells Dana how when Jim wanted to go skydiving, she supported him, and even bought him a helmet that said Geronimo Jim, because she loved his adventurous spirit.
Jim never went. In fact, he completely forgot about it.
Since this worked so well, Dana tried it, but she forgot a crucial piece of information - she didn't change any of the words. And when Jim and Ryan talked about the details, they realized that the two had been talking, and they knew that they had been had, so not only does Ryan want to go more than ever, Jim wants to go skydiving again, and now it's on.
When that happens, Dana gets nervous, but Cheryl just realizes that she needs to up the ante.
So she says that the girls need to go skydiving too, and that will make Jim be protective of the mother of his children, and then he won't want to go. Unfortunately, she doesn't seem to know Jim very well after all these years, because he bluffs her right back, and then everyone ends up on the plane (along with flight instructor Robert Belushi).
In the end, Jim goes, Cheryl goes and then Ryan and Dana push Andy out so that they can join the mile-high club. I guess that's enough excitement for them.
