Dexter is a 4-year old, stuck up jerk. He works in his "laboratory" all day because his good for nothing sister Dee-Dee always bothers him. After a DNA test, it was discovered that Dexter is the son of Dr. Robotnik. Dexter is always in his laboratory working on his greates inventions (which mostly involved porn), then forgetting them and throwing them away.
He once invented a "future-viewing" machine, and used it to look into the future. There, he saw Drew Pickles and Barney getting married, as well as his parents commiting suicide. Dexter then destroyed the machine when he saw too far into the future, and saw very disturbing images that was burning into his eyes, which is why he needs glasses. It is unknown at this point if the machine actually worked, but it is very likely.