In "Unpleasant Surprises" Jeff gives this nice bit:
"I'll never admit this to his face, but Adam's a good friend."
Jeff, Russell and Timmy then throw the bachelor party for Adam in the train that's stopped on the tracks and it's a success.
The final episode is full of them. Jeff and Audrey have their kid via their surrogate and Jeff promises to his new child that he'll be the best dad he can, Adam and Jennifer finally get married and Russell and Timmy have a green card marriage since Russell didn't file the paperwork for Timmy's work visa properly and didn't want him kicked out. Then it turns out that Audrey's pregnant too, which is a surprise since it was supposedly medically impossible for Audrey to get pregnant.