I've been at this since Beta. I gave up on the ultimate challenge until I worked out the Principi sen Fedex ending. But in all my playthroughs I made it a point to gather up all the lost critters. Making it a point of filling my menagerie. Either I'm missing a pet somewhere, or there is no achieve (hidden or otherwise) for this. Help Eder-wan Teylecg, you're my only hope.