There are normal boos as well as character boos (King Boo, Lady Bow, and Peeka & Lahla) in the lora. Triggers for each:

Normal Boo: B00

Bomb Boo: B0mb00, black skin, yellow eyes

Lady Bow: L4dyb0w, green body, red bow, hair bow

Peeka: P33k4, fake rabbit ears

Lahla: L4hl4, fake cat ears

King Boo: K1ngb00, crown, blue tongue