Why limit it? Make it a full fledged animated character brand name booster battle royal.
You know the Trix rabbit would get killed. He can't eat his own cereal. The evasive but frail Tucan Sam and The cheerios bee might elude attackers but it's over when someone touches em.
My money in such a battle royal would be on the Lucky Charms Leprochaun...."they're magically delicious!"