Here's how to get all the riddle trophies/medals
Theo Kojack: as the geek is walking back after he stops moving click on him to unlock this.
Hercule Poirot: Equip one silver item and one gold item and this will unlock. The cheapest ones are the coins.
Lt. Colombo: go to the credits and you will see several boards with "The Geek" written on them covering up the devs names. Click on one of the boards several time and it will fall off. Knock down all of the boards to unlock this.
Col. Mustard: do two hell raisers followed by two meteor smashes and this will unlock.
Sherlock Holmes: Make a geek dressed up entirely as a ballerina then use V-P to launch him and this will unlock. (note: this one is a reference to a picture on the internet. look up "sherlock holmes around the world and you will get the joke)