As James Burrows once explained, if Coach was the befuddled father figure of the show, Woody is the naive kid of the group. In this episode Sam tries to step in the role of big brother and still manages to mess it up.
Woody has been killing it in the weekly football pool, and the gang talks him into doing a parlay with a bookie. Woody wants to bet $1000 (his life savings) while Sam tries to talk him out of it. Of course, Woody wins, and Sam reveals to Diane that he didn't make the bet.
This is yet another bar episode, and while the plot isn't particularly complicated, it provides nuance to Sam and Woody's friendship. Diane has a couple funny moments where she tries to help Sam do the right thing:
SAM: While I'm at it, why don't I just tell him that I meant to bet on all on all winning teams since 1975.
DIANE: Can you do that?
The ending (no spoilers) reveals a new aspect of Sam's personality, or rather his shallowness (" We're talking about my car, Woody!"), and concludes in a truly bizarre way. The only subplot - involving Frasier's pedantic corrections of Diane's grammar - isn't anything special, but it's fun to have the Doc around.