I've noticed these things playing 4 way smash (2 human and 2 CPUs to be especific)
1. The CPUs player often go chasing one of the human players and ignore completely the other, when that one dies they go chasing the other until that one dies and so on.
2. CPUs ignore Mewtwo's shadow ball, meaning you throw the shadow ball at them and they don't guard or move or do anything to avoid it, they just let it hit them.
3. CPUs ignore the items, they don't go for them not even the Smash ball.
1. The CPUs player often go chasing one of the human players and ignore completely the other, when that one dies they go chasing the other until that one dies and so on.
2. CPUs ignore Mewtwo's shadow ball, meaning you throw the shadow ball at them and they don't guard or move or do anything to avoid it, they just let it hit them.
3. CPUs ignore the items, they don't go for them not even the Smash ball.