Just so you know, it's actually Majin Buu with two u's, not o's. But keep excepting o's in case somebody spells it that way, which I have seen. Great Quiz!
Actually the O's is the way it's spelled in the Viz Manga series. I try to use the manga names because of the different ways of spelling it for all the different English Dubs (Example, Goku's name actually has four different spellings: Goku, Gokou, Gokuh, and Zero if you want to consider the old Harmony Gold Dub). But I try to make it so it allows all of them type-ins.
Not sure why everyone gets this wrong (I don't think I've ever seen it right). Frieza has 5 (or 6 if you count DB Super) transformations:
1) How you first see him, with his purple armor. 2) slightly larger, no more armor (I'm sure this is the one most forget, but he does call it a transformation, Vegeta even comments on this) 3) much larger, horns grow 4) grotesque form, long head, larger still 5) Final form, white and smaller again
Brawley*
Namek's Head*
1) How you first see him, with his purple armor. 2) slightly larger, no more armor (I'm sure this is the one most forget, but he does call it a transformation, Vegeta even comments on this) 3) much larger, horns grow 4) grotesque form, long head, larger still 5) Final form, white and smaller again