If I include Copycat on my force and choose to exchange with an opposing character 100 points or less, what happens if I use LE Talon's trait on the character:

If Copycat (on my opponent's force) fails shape change or uses regeneration and Talon is still on the map, what happens?

Copycat's trait (for reference):

The answer is right in Copycat's trait:

There is no game effect assigned to that character though. It is being affected by Talon, but nothing is assigned to it.

This is one that needs to be submitted to the official Wizkids rules team. All that can happen here is guessing really and this is an intriguing topic that they might need to check with Game Design on.

If the Pact is a game effect, how is this not?

The pact specifically targets a character. Raptor's game effect does not target. He just places a character on his card.

I have submitted the question to Wizkids for clarification.