Details on Sunday's Season 3 finale of Mad Men are locked down tighter than Harry Crane's bow tie. The teaser at the end of last Sunday's JFK-heavy penultimate episode contained no new footage, and the episode won't even be screened for critics in advance of its airing. Will the Drapers' marriage dissolve? Will Pete and Peggy join Duck at Grey? Will Roger say something obnoxious, yet witty and charming? The last one is possible, but beyond that we can only guess. What we do know, however, is that none of the following have any chance of happening. Hey, in an uncertain world, we'll take any certainty we can.

1. Guy Mackendrick will return to Sterling Cooper in order to streamline the workforce even further in advance of PPL selling it. He will immediately get his other foot run over by a riding mower. The weird thing is, this time…no one will be driving it.

2. In a last-minute attempt to save Sterling Cooper from dissolution, Don Draper will dig deep and create his most successful ad campaign of all time. The episode will close with Don going over the storyboards for the ad with Peggy, saying, "Let's make the breasts bigger on these two when the guy sings, '…and twins!'"

3. Betty Draper's plans to run away with Henry Francis are nixed when the real Don Draper mysteriously returns from the dead. Betty will ultimately decide that it's a bigger "eff you" to Don to marry Zombie Don than Henry.

4. Pete and Trudy Campbell will take part in another delightful dance number. We figure there's absolutely no way that the writers can contrive to get them to repeat their triumphant Charleston performance from "My Old Kentucky Home." But mostly, we're just putting this on the list of things that won't happen in order to tempt fate. Prove us wrong, Matt Weiner. Prove us wrong.

5. Don will join his family for a long, tense meal of onion rings at a local diner. The scene will end suddenly, leaving many to believe that the implication is that someone came out of the bathroom and shot Don, or possibly came out of the bathroom and fired him. The scene will be scored to Journey's "Don’t Stop Believin'," despite the fact that Steve Perry was 14 in 1963.

For the next five Mad Men season finale twists you won't see, click the Page 2 link below.