You choose which spells to cast (if any) as Kefka's last ability resolves
According to the official Secrets of Strixhaven mechanics breakdown, when a Creature (it could be any permanent, but in Secrets of Strixhaven every card with Prepare is a Creature) becomes prepared , "a copy of its Prepare spell appears in exile
Card Set(s) -Memorial Collection- [EB-01] CARD VIEW EB01-044 | C | CHARACTER Funkfreed Attribute Slash Block icon 2 Effect [Activate: Main] You may rest this Character: Up to 1 of your [Spandam] Characters gains +3000 power during this turn
There are endless variants of these cards that grant multiple bonuses, draw you a card in addition to the effect, or both
I just love that you can channel this bad boy for a bit of damage
Whenever equipped creature deals combat damage to a player, you create a 2/2 green Wolf creature token and that player mills ten cards