Sleepy Furball

Sleepy Furball enters the battlefield tapped.
Sleepy Furball doesn’t untap during your untap step.
Whenever one or more creatures attacks you or a Planeswalker you control, untap Sleepy Furball and Sleepy Furball gets +3/+3 and gains Firststrike until end of turn.
{t}: Sleepy Furball deals damage to target creature equal to its power.