You control a face-down creature whose front face is a permanent card.
You have enough mana to cast
Switcheroo.
Steps
Cast
Switcheroo by paying its mana cost, giving control of
Karlov Watchdog to an opponent.
During the opponent's turn, activate
Phyrexian Altar by sacrificing a face-down creature you control, adding one mana of any color.
When the creature dies,
Yarus's second ability triggers, returning it from your graveyard to the battlefield face-down as a 2/2 creature, and then not turning it face-up due to