Okay, so was it in Nationals where Rachel said that she and Finn were getting married in a church with a rabbi as officiant?
I can't imagine a rabbi agreeing to officiate a wedding without doing premarital counseling first. So, I want to see what goes on in those sessions, and why the rabbi agrees to do the wedding. (Even better, the rabbi doesn't, and they have to find another officiant.)
AU variation: It's an AU where Puck is 10-20 years older. And he's the rabbi. (mimiheart has given me many convincing reasons why Puck would make an awesome youth rabbi; maybe he's a youth rabbi in this AU and gets stuck with the teen weddings.)