When do you choose a pouncing character?

For instance, could I choose Mimic? Late dial he meets the criteria. Or do I have to choose a character who meets the criteria on his opening slot?

Thanks....
-d

BTW, I mean that Mimic could only use it after he meets the criteria, not before.

You may choose someone that meets the requirements at any point on the dial. Otherwise, Automatic Regeneration would be a pretty useless feat, as noone has Regen on thier first click.