Horton, Who Hears

Double strike, vigilance, trample
Whenever Horton, Who Hears deals combat
damage to a player, you may tap target creature
that player controls. It doesn't untap during its
controller's next untap step.
{t}: Tap target permanent that dealt damage to
Horton, Who Hears this turn. It doesn't untap
during its controller's next untap step.