You know what I like about squares? They got 4 sides. You know what I like about triangles? They got 3 sides. You know what I don't like about circles? My mom was killed by a circle.

Repeat over and over with different punchline. Stretch and slightly alter the set up over time. Commentary between on audience reaction.

My grandmother was raped by a circle

A circle injected my dog with heroin

Ask the audience

A circle beat me up and took my lunch money.

They never take out the trash

I slipped and fell and broke my collarbone after a circle pulled a banana peel with a string right under my foot.

They're ugly and stupid and mean mean mean

A circle invented war

A circle killed Genghis kahn and blamed hitler

I sold my soul to a circle for this joke. I know what you're thinking. He said no refunds.

20 million dollars a day spent in Afghanistan

You know what I like about avocados?  They have 4 sides. You know what I like about Cantaloupes?  They're orange on the inside. You know what I don't like about circles?

Finish by blaming why I don't like circles because I'm bigoted and my upbringing. Apologize to all circles and circles in the audience I may have offended. I know that many of you have not raped my grandmother. Although it is difficult to tell you apart. Every circle I see is just a reminder of that circle that beat my dog up and injected my him with heroin.