If you cast a 2/2 Grizzly Bears, for example, you may then search for any creature with total power and toughness 4. It can be 0/4, 1/3, 2/2, or 3/1.

The game checks the power and toughness of the creature that just entered the battlefield as it exists on the battlefield. That might mean it's impossible to get another copy of that same card. For example, a Triskelion on the battlefield is 4/4, but a Triskelion in your library is 1/1. The power and toughness might also have been affected while the triggered ability was on the stack (such as with Giant Growth, Sudden Death, or Ovinize).

If the creature that entered the battlefield has left the battlefield by the time the ability resolves, use the power and toughness of that creature as it last appeared before leaving the battlefield.

If the total power and toughness of the creature that entered the battlefield is less than 0 (due to Bewilder or Sudden Death, for example), it is treated as 0 by Wild Pair. For example, if a creature was -2/1, you could search for a creature with total power and toughness of 0. If either the power or toughness is less than 0, but the total is greater than 0, use the actual total. For example, if the creature is -1/3, you could search for a creature with total power and toughness of 2.