Alright, I was thinking... (Totally fake sample info included)
Code:
Event Name: Ash Ketchum
Sprite: Ash overworld
Area: Pallet Town House #1
Location: Sitting at table
Movement: Stationary
Trigger: Talk to (as opposed to walking on or activating upon entering the room)
Script: Before beating the E4, he says "You should beat the E4!"
After beating the E4 but before catching Mewtwo, he says "You should catch Mewtwo!"
After catching Mewtwo, he disappears.
Too much? Not enough?