Title text: I'm a solipsistic conspiracy theorist. I'm sure I must be up to something, and I will not stop until I find out what.
The punchline refers to an old grade school/middle school prank (Urban Dictionary: pen 15 club, Pen 15.) You'd typically walk up to an unsuspecting schoolmate and ask him if he wants to join the Pen Fifteen club. You'd tell him that to join, you merely have to write the club name on him. You'd then write "PEN15" on his hand or arm, and everyone would laugh at him because it looks like "Penis". In this case, Cueball fell victim to this prank as a child without ever figuring out the joke (maybe because they got him to write it himself on his arm and he literally wrote "Pen Fifteen" instead of "Pen15"). Later on, he created meaning and conspiracy out of two completely unrelated, coincidental events, and resultantly burned someone's house down. All because he so badly wants to be part of something bigger.
As for the title text, solipsism is the philosophical idea that only your own mind is sure to exist while other minds can't be really known and so those other minds are not proved to be real.
- [Cueball and a child are talking.]
- Child: What's that on your arm?
- Cueball: The mark of a secret society.
- Child: If it's secret, why tell me-
- Cueball: Because I know nothing. I can't betray them because I don't know who they are. I was chosen by an agent 20 years ago. That was my first and last direct contact. It's safer that way.
- Six years later I found a piece of paper in the street with an address on it. The next day I found a can of kerosene in my garage that I'm sure I never bought.
- [The panel represents these actions by highlighting the mentioned objects in a world of gray.]
- I didn't know whose house it was. I just knew that I'd been given my orders. And I carried them out.
- [A dark figure is silhouetted against a flame.]
- Cueball: I don't know who or what we're fighting.
- Cueball: Maybe we're the bad guys.
- Cueball: It doesn't matter to me.
- Cueball: It's enough to know that there are forces working beneath the chaos of life, and I'm a part of them.
- Cueball: That whatever this "pen fifteen" club is,
- Cueball: I'm in it.