When Bart comes back to the time travel car, Mr. Burns and Smithers are walking on the sidewalk.
List of Homers:
Teen Homer Simpson.
Caveman Homer (actually Renaissance Homer).
Space Alien Homer.
Egyptian Slave Homer.
It took 15 days to catch the strange being who was doing weird things in the house.
There were 8 cameras up around the Simpsons' house; Camera 1 was in the Living Room, Camera 2 was in the Foyer, Camera 3 was in the TV Room, Camera 4 was in the Kitchen, Camera 5 was in the Master Bathroom, Camera 6 was in Bart's Room, Camera 7 was in Lisa's Room, and Camera 8 was in Maggie's Room.
The music in the scenes with the Mayan Indians is based on Apocalypto.
Lard Lad, a reference to the Big Boy restaurant statue, is holding a corn on the cob.
"Treehouse of Horror VI": Maggie's pacifier saves the day (Maggie plugs her pacifier into the Groundskeeper Willie bagpipe spider/Maggie's pacifier stops the black hole from sucking up everyone in the world), giant statues destroy Springfield, use the Lard Lad Doughnut sign as a weapon and knocks on the Simpsons door which Homer answers, and Homer is sucked into a black hole.
"Lisa the Simpson": Homer has a lot of relatives (or, in this case, past selves) who look, sound, and act like him.
"Treehouse of Horror": Garbage is thrown into a black hole leading to another dimension; The Simpsons are haunted by an invisible force in their house.
"Treehouse of Horror X": A Simpsons Halloween episode features a story about the world coming to an end based on an alleged apocalypse said to happen in real life (the Y2K disaster/the end of the 13th Baktun on the Mayan Calendar).
"The Way We Was": Homer getting in trouble for smoking in the high school bathroom, Homer and Marge meeting in detention, and Marge dating Artie rather than Homer (though the events in this episode show what would have happened if Marge never met Homer and went with Artie).
"Treehouse of Horror V": Homer travels to an alternate reality where his family is rich and successful and lives in a nicer house than the current one; a Simpson male travels through time.
"The Ziff Who Came to Dinner": a parody of "found tape horror movies" (where the whole movie is video footage of people trying to find a hidden horror and the video ends with the people either missing or dead from suspicious circumstances) is shown (Bart and Lisa's attic expedition is from The Blair Witch Project while Homer taping the poltergeist in the house is from Paranormal Activity).
Mayan Mayor Quimby says that the destruction of earth would be Obama's fault, but how he know that there is going to been a president named Obama in 2012 even though is the 5th century in that time. But maybe because they are mayans they can tell the future.
The Greatest Story Ever Holed
Before Cletus's house is sucked up by the hole, you can see that the house is a double decker one (as you see that there is a window in the top of the house). But as the hole sucked it in, the hole didn't suck the second floor and the things in the second floor.
When Lisa' tears are being sucked in, the hole is in front of red railings. But in the next scene, it is floating in the mid-air.
When the Simpsons are eating breakfast, they are in their pajamas. But when they open the door, they are in their trademark outfits.
Lisa says that what goes into a black hole never comes out, but then later Bart's math homework comes out after going in. This was just a joke about how Bart doesn't want to do his homework.
The black hole is too big for Lisa to get so close to it. This could have been done on purpose so the black hole would be visible.
When the Simpson family is standing in front of the house, the door is open, but when the house is sucked by the blackhole, the door closes itself.
In Unnormal Activity, Devil Moe says that Marge gets 30 years. 2012-30=1982; In there Marge is just a young child, but in Bart & Homer's Excellent Adventure she's already in high school. Hence the past time year Bart travelled to 1974.
Milhouse is seen sleeping in Bart's Room and Lisa's Room at the same time (Camera 6 and Camera 7). This can show how Milhouse is best friends with Bart and is in love with Lisa.
Bart & Homer's Excellent Adventure
When Homer shows all the Historical Homers, Two Head Homer, Punk Homer, Egyptian Slave Homer and Washington Homer are not on the line of Homers. But later they appear (maybe young Homer brought them after he brought the other Homers).
Just after Bart leaves the comic book store, Homer from 1974 is seen walking into a store next door.
Plot Hole: If Marge married Artie Ziff instead of Homer, then Bart, Lisa and Maggie shouldn't have been born (or, at the very least, look different from how they currently look), but this episode is non-canon.
Another Plot Hole: Homer and Marge are apparently older than they look. Bart goes back to 1974 when they were still in high school. If this were the case, then they would be in their 50's in the present. (But again, this episode is non-canon and they don't age anyway.)
Marge says that 20 years ago, she would have chosen love when she realized that Homer was the one for her all along. However, 1994 is 20 years after 1974, and it is 2012, 38 years later.
As Homer and Marge go to investigate a loud crash, Homer doesn't go through the same door as Marge, it seems he goes through an imaginary door that's on the other side of the mirrors and drawers. There is only one door that leads to the master bedroom usually.