M: "Ha ha ha! Everyone laughed at my dreams of world domination? Well say hello to Deathbot! Deathbot, show the people why you're called that!"
D: ARRGH! OHHH! I'm dying! I'm dying!!
M: Well, this is embarrassing!
B: Don't give up your dream. Just climb right back up on that horse!
This comic is a really old Brewster Rockit comic. The comic contains two jokes: one is the fact that "Deathbot" ended up being a robot which had the primary function of dying (living up to his name literally), and the other is the consolation that Brewster offers Dr. Mel (which is humorous because it was unexpected, since Dr. Mel just tried to kill him with the aforementioned robot).
There is another thing that is humorous in this comic: the character Dr. Mel is an archetypal mad scientist, which would be (based on western culture) expected to be evil, insane, and not the friend of the protagonist. Dr Mel is only two of those things in this comic.