School is back in session across the United States as well as at our  favorite bar!  Rebecca's favorite college professor returns to Boston only to divert her focus to continuing education with Sammy.  Plus we get to watch the legendary Alex Trebek guest star as Cliff's bucket list gets reduced by one as he earns a spot on Jeopardy!  All that plus Sam's little black book has been stolen and the gang pulls out all the stops to garner its return!  Head on down to roller rink, order a couple sodas and enjoy "Sammy and the Professor" and "What is...Cliff Clavin?"!  (S8E13 starts