Select "Cheats" at the main menu. Then, enter Down, Left, Up, Right, Down, Left, Up, Right, Down. Enabling codes will disable game saves. If you complete a new level with the cheats on, you will not be able to save and must then repeat the levels without using codes.
Michigan J. Frog Trophy: In the Assembly Line Insanity level, go to where all the black knights are before you trigger the switch. The trophy is hidden in a breakable section of wall on your way to the platform.
Porky Pig Trophy: At the end of the Muddy Evil Forest level, before you reach the Big Black Knight, get on top of one of the houses. The trophy is hidden in the tree top.
Road Runner Trophy: Get to the swinging pendulum section in the Pyramuddle level. Go all the way across to the opposite side of where you entered. The trophy is hidden in one of the breakable boxes.
Tweetybird Trophy: Near the end of the Whack Tastic Robo Bash level is a door marked with the word "MONSTER". The trophy is somewhere above that door.
Wile E. Coyote Trophy: Go up the hill at the start of the Volcano Way Out level. Continue until you find the first tree on the left. Fall off the ledge to the left to find the trophy.
Yosemite Sam Trophy: Get to the part of the Low Noon level where you meet the first Big Cowboy. Go back the way you came from, past the tracks to the right. The trophy is hidden on top of one of the houses.