In Luigi’s Mansion: Dark Moon on the Nintendo 3DS, there are several bonus missions you can unlock to play through.
The bonus missions are unlocked by capturing the Boos in various different levels. You’ll start to capture the Boos in Gloomy Manor, however the game doesn’t really explain what you receive by capturing them.
Here are the bonus missions you can unlock, and where to capture the Boos to unlock them.
Gradual Infiltration – Capture all five Boos in Gloomy Manor
Hostile Intrusion – Capture all 5 Boos in Haunted Towers
Outlandish Interruption – Capture all 5 Boos in Old Clockworks
Severe Infestation – Capture all 3 Boos in Secret Mine
Terrifying Invasion – Capture all 5 Boos in Treacherous Mansion