This may be the first episode to do fart jokes. Actually in the eleventh-season premiere episode Beyond Blunderdome, Marge says Bart's name when he burps and a fart noise is heard (which came from Marge because she said, "Well, that shut me up").
God returns from THOH XVI (Unless you count THOH XVIII where Ned mentioned him.)
Jimbo, Dolph and Kearney throw a Skunk at Bart's old body.
The second story, Dial D for Diddily, was based on the TV show, Dexter.
Dial D for Diddly is a pun on the 1954 crime thriller film, Dial M for Murder. This is the third THOH segment that references this film. The first was Dial "Z" for Zombies in Treehouse of Horror III, second was Dial 'M' for Murder or Press '#' to Return to Main Menu in Treehouse of Horror XX. There is also an episode called Dial "N" for Nerder.
The third story, In the Na'vi, was based on the science fiction film, Avatar, for example Hilarium is parody on Unobtainium.
In the Na'vi is a pun on the 1941 film, In the Navy. The Na'vi is the alien species in Avatar.
In the third segment, Superintendent Chalmers is in an exoskeleton that look exactly the same as the exoskeleton called The Commander from ios game Sentinel 3: Homeworld.