Hidden Conditions:
You have to defeat Perfect Cell within 3 minutes to trigger the hidden conditions. If you defeat him within the time limit, he'll transform to his possessed form and will become more powerful. He'll be pretty hard to stagger in this form so you may have to rely on your Ki Blast Supers and Ultimate attacks to safely damage him. Don't hesitate to use items if necessary.
Is it random?
Im killin this guy under 3 mins both forms and I cant get it to drop