The League of Oddfellows
A cracker-jack is someone who is agile, graceful, and light on his feet. He has excellent hand-eye coordination and reflexes. He might be an acrobat, a sprinter, a dancer or an archer.
Cracker-jacks use the rules for Fast Hero from d20 Modern, with the following exceptions:
Hit Die: d8
Skill Tree: 4-up
1st Level Bonus: +2 to Reflex saves and Acrobatics.