Mario often takes the appearance of certain animals and objects in his games. These have included a frog, a penguin, a balloon and even a metallic version of himself. These lighthearted and whimsical transformations give Mario different abilities and make his games fun to play. The different forms that Mario takes make no statement beyond the games themselves.
And there it is, plain and simple. Mario’s transformations are for fun and have no secondary meaning whatsoever.