Ronald being able to get past all of Franklin's tests is awesome in its own right. This especially applies to when he's able to answer the riddle, prompting Franklin to have a Villainous Breakdown.
Franklin is actually a pretty awesome antagonist since he's created an entire test in his father's mansion and able to get ahead of the gang for most of the events.
The Legend of Grimace Island
Ronald manages to transform a ship in a bottle into a fully-sized, seaworthy vessel.
Ronald saves the gang from a giant squid by tying its mouth shut with one throw of a rope.
Grimace manages to prove himself in "Legend of Grimace Island", when, following a failed attempt at stopping them, he courageously manages to force One-Eyed Sally and Blather into surrendering the treasure and leaving. By using a feather and the threat of Tickle Torture, which One-Eyed Sally had previously used on him, no less.
The Visitors from Outer Space
Ronald saving Grimace by hitching a ride on a comet.