A Jekyll & Hyde type transformation that lets out the dark side of a usually sensible and respected memeber of the community after they've sipped an alchoholic beverage(usually Stella).
Probably best not to approach them cause they're known to partake in random acts of violence and mischief.
Pete: "Did you see Larrikin Lu was on the rampage again last night?"
Ad: "I noticed all our windows were smashed so i guessed he'd come back."
Pete & Ad: "Oh shit!"