Here is the full list of all 19 Spooky Bonus achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Set off 20 bonuses on a single level.
Find a black cat.
Score 5000 in a single level.
Collect a bag of coins.
Chain react 3 bonuses at once.
Match 5 shapes at once.
Beat the game in Relaxed mode.
Beat the game in Timed mode.
Purchase all of the house decorations.
Score 8000 in a single level.
Use all 6 powerups on a single level.
Upgrade a powerup to level 3.
Purchase the Grey Alien decoration.
Reach the Dungeon level.
Reach the Asylum level.
Reach the Crypt.
Chain react 6 bonuses at once.
Set off a Garlic Bomb
Collect 10 coins on a single level.