Here is the full list of all 16 Graveyard Shift achievements.
Complete game in easy mode
Complete game in normal mode
Complete game in hard mode
Kill three ghosts with one mushroom
Collect 250 mushrooms
Collect 500 mushrooms
Collect 1000 mushrooms
Score a 100
Score a 1000
Score a 10000
Kill 100 ghosts
Kill 250 ghosts
Kill 500 ghosts
Throw 100 mushrooms
Throw 500 mushrooms