Hyjack Cubbies

Whenever you exert a creature, you may
pay {r/w}. If you do, mature Hyjack Cubbies.
(To mature this creature, exile it. If you do, search your library for a non-Young creature card that shares a creature type with it. You may cast it by paying the difference in mana costs between it and this creature. Then shuffle your library.)

Witnessing the trials the adults put themselves through rapidly readies the youths.