Matt Groening

Cartoon characters with overbites
His characters' middle name often begins with the letter "J", e.g. Homer J(ay) Simpson, Bart J(ojo) Simpsons, Philip J. Fry
Homages to classic films
Often works his initials into a drawing. For instance, Homer Simpson has hair forming an M and ears shaped like Gs
Slapstick humor

His parents were Homer and Margaret, and his sisters were Lisa and Maggie.
The Comic Book Guy, a character in Die Simpsons (1989) is a version of what Matt Groening considers himself to be like.
He decided to give the Simpsons characters yellow skin to attract and deter channel surfers.
He said in a 1990 interview, that Bart Simpson was based partly on Dennis the Menace and himself as a child. Bart's original name was to be 'Matt' but he changed it because it sounded too closely-related. The name Bart is an anagram of 'brat'.
Was once subjected to a strip-search by airport security who considered him a suspicious character. As he was led away, a little boy said, "Ha, ha!" like Nelson on The Simpsons. Groening found the boy's mockery the most irritating thing about the incident.

I'm a writer who just happens to draw
[on the Simpsons bar Moe's Tavern and taverns in general] I was always frightened by taverns. They just seemed like very unpleasant places to go. And there is nothing nice about Moe's Tavern. It's just a creepy, dark place. And there are never any women in there.
[when asked "Is there a God?"] If there is, all evidence indicates that He hates me.
On the television series [The Simpsons], a joke has to pass muster about 100 times before it gets on the air. On the movie, it's probably 1,000 times. There are jokes that were funny the first 350 times, and then, the 351st time, we go, "Ah, I'm kinda tired of that", so we change it. And what stays in are the most obvious, dumb, visceral, knee jerk, mayhem gags. Any time a character falls down, gets kicked in the face, hit in the head... anything involving head injuries. We work so hard on the wittiest dialog, involving sophisticated references to books and movies, and then what gets a laugh is Homer belching after drinking beer. It keeps you humble.
The history of television has traditionally been not to do anything that would scandalize Grandma or upset Junior. Our solution on The Simpsons is to do jokes that people who have an education, or some frame of reference, can get. And for the ones who don't, it doesn't matter, because we have Homer banging his head and saying, "D'oh!".