The tube Abe is in is a reference to the tube that appeared in the very first Futurama episode.
Maggie's performing style as a singer may be inspired by Lita Ford and/or Lady Gaga.
Lisa married Milhouse but seems to have keep her maiden name, since her daughter's full name is Zia Simpson. Lisa's Christmas card is captioned "Merry Christmas from Simpson-Van Houten-Simpson-Simpsons" which may imply that Lisa kept her last name, Milhouse took on the hyphenated Simpson-Van Houten surname and Zia has her mother's last name.
Martin Prince has undergone a sex change to become Martha Princess.
Just like previous flash-forward episodes, Maggie never says anything. The robot nurse told her not to say a word for the duration of her pregnancy from that point forward, due to new research discovering the the umbilical cord is also a vocal cord. After she has her baby, she does open her mouth to speak when Grandpa asks who her baby's father is, but he cuts her off. However, she is shown to be a world famous singer, enhancing the gag through irony. Similar to "Lisa's Wedding", where it's revealed she is as a good singer, but gets interrupted before she can use her talent, along with being cutoff whenever she tries to speak, and being described as never shutting up.
On Maggie's Christmas Card, it is captioned "Maggie Simpson: The Voice of Her Generation".
Lisa also asks Bart if she should have married Nelson, indicating that they were once together. This also indicates that Nelson proposed to Lisa sometime before she married Milhouse, most likely at the same time as Milhouse had proposed. Later in the episode, when Lisa is going through her friend requests in the Ultranet, Nelson's request appears and he asks her is her marriage is still dead and unfulfilled. Lisa probably described her marriage like this to Nelson in her phone calls to him. She rejects his friend request, however.
Jenda, Bart's high school girlfriend from Future-Drama, appears in a picture. It's revealed that she married Bart, had two children with divorced him, and married her new boyfriend without Bart knowing.
At some point, paper cash will no longer be in use, according to Apu.
Schools at this time period are now banned from talking about the meaning of Christmas, according to Bart's sons.
The name of the father to Maggie's daughter is never mentioned.
However, in this episode's sequel, "Days of Future Future", Maggie makes a cameo at the Guilded Truffle, where she is sharing a drink with Gerald Samson, meaning there is a good chance that he is the father.
When Lisa dates girls in college, she has shorter hair, probably due to the stereotype that lesbians have short hair.
Originally, this episode was supposed to be the series finale, as Fox was considering cancelling the show due to money issues stemming from advertising the show. Once the issues were resolved with a pay cut for all involved with the show, the series was greenlit for seasons 24 and 25.
In the description of the Sky 1 airing of the episode, there is a mistake saying it is the fifth episode of Season 23, not the ninth.
There are only 42 octuplets of the octuplets. If all of the octuplets had octuplets, there should be 64. This is either a goof or not all of them are there.
Grandpa's hat is slightly lower in the reflection of himself.
Carl (with Lenny's brain) tells Lenny (with Carl's brain) to stop making Lenny fat, but in "Sweets and Sour Marge", Lenny is one of the people in the sugar, and even looses some of his teeth. In the thirty years that passed, it's possible Lenny chose to go on a diet.
When Lisa enters the Ultranet she comments that it is Dr Seuss' birthday as indicated by the design of the Google page. Dr Seuss' birthday is March 2 and this episode takes place over Christmas.
When Lisa first goes into the Ultranet there are two of the same people in one scene.
Despite Edna being killed by Homer, she appears at Lisa's Ultranet friend requests. However, it could be possible she sent the request before she died. This gives off the impression that Lisa isn't a very frequent Ultranet user.
Zia's drool is missing when we see her and her mother are in the table while both are on the Ultranet.
Lisa and Homer refer to Prince Harry as one of history's tyrants, strongly implying that he eventually became King, although they still refer to him as a Prince rather than King.
The family is grown up in this episode but remain the same voices.