Quick!
Explanation
The Joke
A person rushes in shouting "Quick! I need a ball point pen, a rubber band, and a five-dollar bill!" with great urgency. A bystander helpfully offers up the money: "Here! I have the money!" The urgency and the specific list of items suggest some kind of MacGyver-like emergency improvisation.
In the second panel, we see the person walking away with the items, calmly remarking: "This is way easier than mugging."
The Humor
The comic is a simple but effective bait-and-switch. The setup leads the audience (and the victim) to assume the person is in an emergency situation and needs these specific items for some ingenious purpose -- the classic action-movie trope where the hero improvises a solution from random objects. The urgency creates social pressure for bystanders to help without questioning.
The punchline reveals that there was no emergency at all. The person simply discovered that if you ask for things with enough urgency, people will just hand them over -- making the whole performance essentially a low-effort con. The inclusion of mundane items like a pen and rubber band alongside the five-dollar bill makes the scam seem less suspicious, as a real mugger would presumably just ask for money. The comic highlights how social engineering and the manipulation of urgency can be more effective than brute force.