Ryan tricked Wilfred into going to the vet this week, but Wilfred got his revenge.
As he was going under, he whispered "Jenna has a dick..." causing Ryan to think Jenna actually has a dick. This led to an awkward conversation with her, as Ryan tried to learn if it was true or not.
In the end, though, we learned that Jenna has a dick FOR A BOYFRIEND. Chris Klein made his first appearance in that role, as Wilfred had a good laugh at his friend's expense. But these two also bonded more and tried to teach each other a few lessons.
Wilfred put it well in the end: the door is now open between them.