Trogdor 3-Dungeon:
To unlock the Trogdor 3-Dungeon, beat the game and then go to the Trogdor Machine.
Redcoat Ghost patrol:
Do the following to repeatedly gain 100 points. After Trogdor get out of the machine go to the House of Strong. Help the four colonel ghosts to get the ghosts out of the hose. Go outside to the field and shoot the Redcoat Ghost with the light musket. You will gain 100 points and this can be repeated.
Cheat laughs:
After Trogdor is out of the machine and the ghosts leave the House Of Strong, go to a redcoat ghost found somewhere in the field. Take out your light musket. If you miss it, The Cheat will come out of nowhere and laugh, similar to how the dog on Duck Hunt appeared.