Mesa is a young mustang colt that Aztec encounters in the episode "Wild Horses". He is kind to Aztec when he first meets him, although this does not agree with the other mustangs. Mesa is FIVE years old and his mother is two years old.
After Aztec leaves, Mesa follows him to help him find some good food. Suddenly, a bear charges out of the woods, and Aztec tells Mesa to run and save himself. Luckily, Mesa brings his herd to rescue Aztec.
After apologizing, Chako, the leader of the herd, asks Aztec if he would like to join the herd. Aztec turns it down (much to Mesa's disappointment), explaining how he misses his old life. Mesa says goodbye to Aztec and leaves, never to be seen or mentioned again.
Mesa is very kindhearted and playful. He is helpful and will do anything for his friends, even if he puts himself in danger.