The episode begins with the family in the town square. Roger is horribly depressed and drunk, complaining that since landing on Earth sixty years ago he's accomplished almost nothing; Stan, however, is overjoyed, until he finds out that the Christmas Tree has been banned due to its religious nature. He is further dismayed when more signs of secularism occur---the clerks at the mall aren't allowed to say "Merry Christmas," and the town goes so far as to rename the annual attacker, the Christmas Rapist, the "Holiday Rapist." Stan blames the whole thing on Jane Fonda---his logic being that her going to North Vietnam revitalized the "dying" hippie movement, and that since yesterday's hippies grew up to be modern liberals, modern liberalism is her fault. Stan finally becomes so enraged that he destroys the tree and the presents; the kids and Roger are horribly sad, and Francine is so mad she banishes him to the couch.
That night, Stan is visited by the Ghost of Christmas Past (a former Tooth Fairy named Michelle), who takes him back to 1970. Stan, however, runs away from her, in an effort to find Jane Fonda in order to assassinate her, thus changing the future. The Ghost, unsure where he has gone, goes back to the present to get Francine; the two then return to the past to find Stan.
Stan has tracked Fonda down to the set of Klute, where he finds out that Donald Sutherland was the one who led her to politics, and changes his plan to assassinate him instead. He finds Sutherland at a Hollywood party, where he happens to meet Martin Scorsese and convinces him to give up drugs. Francine and Michelle then grab him and bring him back to the present, where they are shocked to discover the street desolate, with Soviet tanks patrolling. They eventually figure out what has happened---by getting Scorsese off drugs, they stopped him from ever making the movie Taxi Driver; as a result John Hinckley, Jr. never saw Jodie Foster in the movie and became obsessed with her, which resulted in him never trying to assassinate Ronald Reagan. This dented Reagan's popularity in the 1984 election, as the near-death experience made him appear stronger; in the new reality he thus lost to Walter Mondale, who then surrendered the country to the Soviet Union just 47 days into his Presidency. The group then goes back to attempt to fix what Stan did.
Stan decides to make the movie himself; however, he quickly alienates Robert De Niro and decides to make the movie with John Wayne instead. Stan and Francine follow Hinckley into a movie theater and watch the new Taxi Driver behind him. After the movie is over, Stan asks Hinckley what he thought of the movie, and he says it was alright. Francine then asks him if he thinks Jodie Foster is attractive, and he reacts very badly to this, pointing out that she is 12-years-old. This means that the future remains unchanged. The Ghost then transports them to March 30, 1981, and tells Stan that the only way to fix the future is if he shoots Reagan instead. Stan is shocked; he is unable to shoot his favorite president. Francine reminds him how much he wanted Christmas, and points out that it wouldn't exist at all if the Soviets ruled; Stan replies that he doesn't care about trees and presents, but would be happy as long as he had Francine and the kids. The Ghost then informs him that in the alternate future Francine and Stan may never meet, meaning also that Steve and Hayley won't exist. Stan then decides that he must shoot Reagan, and shoots him. Just as he does, the two suddenly transport back into their bed on Christmas morning, 2006.
The two are relieved to find out that history is back to normal, and after fixing the presents and tree, the family enjoys a happy Christmas. The Ghost appears to Stan one last time to give him a gift for saving her job -- a brand new gun she says she bought the previous night. When Stan asks how that is possible, as the Brady Bill requires a week waiting period, she informs him that he only shot Reagan and not Brady, meaning that buying guns is incredibly easy. Stan rejoices that he changed the future for the better (in his own eyes), and says "this is the best Christmas ever."
In a subplot, Stan buys a "Best of Disco" cassette for Roger. When he goes back in time to 1970, the tape falls out of his jacket and is found by Roger. Playing it to executives, Roger becomes fabulously wealthy by inventing the Disco era. However, in 1981, disco becomes "dead" and Roger loses everything. Upon returning to the future, Roger still talks of his time as the inventor of disco and the episode ends with that timeline still in effect.
- The picture that the carolers show to Stan of the Holiday (or Christmas) Rapist resembles the elf who photographed Hayley and Steve sitting on Santa's lap.
- During the flashback on how the present was changed, Hinckley's last name is misspelled on the name of his ice cream business. It is misspelled as "Hinkley".
- Leonid Brezhnev died in 1982 in the prime timeline, making it unlikely that, in the alternate 1985, Walter Mondale could surrender to him.
- "The Most Adequate Christmas Ever"
- "Rapture's Delight"
- "For Whom the Sleigh Bell Tolls"
- "Season's Beatings"
- "Minstrel Krampus"
- "Dreaming of a White Porsche Christmas"
- "Ninety North, Zero West"