Title text: You can do a lot better than 1% if you start keeping track of the patterns in what numbers people pick.
A psychic is a person who claims to be able to access information that is beyond normal sensory perception through extrasensory perception. This information may vary widely in scope and value, ranging from archaeological to the ability to read minds. Cueball describes himself as such a person, to which Megan responds with disbelief because it is a bold and unsupported claim. To prove his abilities, Cueball has Megan think of a random number from 1 to 100, which he then guesses correctly to demonstrate his ability to read minds. Megan is amazed that Cueball was correct, but he simply dismisses her disbelief and wants to go back to pretending to lead a normal life.
The four panels are actually a setup to the real joke in this comic: the final sentence spoken by a narrator. It reveals that Cueball has simply played a trick on Megan and that anyone can repeat it. The joke is that, theoretically, a person can guess a random number from 1 to 100 once in one hundred tries, or 1% of the time, according to the law of large numbers. By playing this trick enough times on enough friends, the trickster is statistically likely to get a number right eventually. Assuming the person whose number he guesses is not familiar with the trick, it will appear as if the trickster is actually psychic. Should this happen, the trickster can then play the joke out as he wants, hence the "it's totally worth it" at the end.
The title text appeals again to statistics. People are poor random-number generators—e.g. being less likely to pick numbers at the extremes or exactly in the middle. Knowing this, the 'psychic' could restrict his guesses accordingly, improving his odds of guessing correctly.
- Cueball: I'm psychic, you know.
- Megan: There's no such thing.
- Cueball: Okay, think of a number from one to one hundred.
- Megan: Okay.
- Cueball: 43.
- Megan: Holy shit!
- Cueball: I try not to let it affect my life too much.
- Megan: Wait, I can't believe this.
- Cueball: Don't worry about it. Forget I said anything.
- Megan: But-
- Cueball: Let's get to the movie.
- Megan: I, uh... Ok, sure.
- This trick may only work 1% of the time, but when it does, it's totally worth it.