Doctor Quandary is the main antagonist of the titular series, The Secret Island of Doctor Quandary.
In the game, he is first seen hosting a carnival and his main attraction, Troggle Shoot, appears to be a huge hit. This is especially since most of his rides are unsafe or expensive. He gives the player a free chance to play. Upon winning, the player receives a special doll. This is no ordinary doll, Dr Quandary explains, and he says they can even come alive. (Dr. Quandary has possessed the dolls to suck the player's soul.) The player chooses which doll they want, and then their soul is sucked in by the doll. They then are transported to Dr. Quandary's secret island, where Dr. Quandary has included a series of puzzles that they have to complete before they are released. These puzzles vary in difficulty, and Dr. Quandary occasionally appears to taunt you with quips and puns.
Doctor Quandary is not so much malevolent as he is deranged and annoying. He never brings direct bodily harm to the player or puts them in peril, but he does deliberately make things even more difficult and frustrating. If you master his puzzles and escape his puzzles, he will even congratulate you.