Where Did The Boos Come From?

[Mariposa Electrique]

Whose were the boos previously? Were they always ghosts?

 

[Red Hood]

Usually you get boos at a liquor store

 

[From The Uncanny Valley]

I was saying Boo-urns...

 

[WeWuzFinns]

Boo is what kkkhosts say when they are scaring away spooks.

 

[MrTroll]

The ghosts of dead goombas, come back for revenge.

 

[stupid frog]

They're a race, apparently.

 

[Smug Chuckler]

They were the Marios/Luigis that died from previous attempts.

 

[zero-who]

I want to say they're dead Toads? Doesn't explain where King Boo comes from, though.

 

[Paulmall Blartcop]

boos did 9/11