Leo (full name Leonardo) is the protagonist of Little Einsteins. At 6 years old, he (as well as June) is the oldest of the group. He is the Little Einsteins' leader and the one who pilots Rocket. He is also Annie's older brother.
Leo has red spiky hair, large teal glasses, and green eyes. He wears a black short-sleeved t-shirt which has an orange streak, orange cargo shorts with large pockets, white socks, and orange and black sneakers.
Also, he made meet-and-greets with people, just like the other Little Einsteins, except Rocket.
- He is the only character on Little Einsteins to wear glasses.
- His skills with the baton include the ability to conduct animals (seen in Our
BigHuge Adventure, where he conducts cows and The Song of the Unicorn).
- His main talent is conducting and his most precious object is his conductor's baton; he never leaves home without it.
- Although he is only six years old, he is tall, in fact, he is taller than Quincy and his little sister Annie (she is the smallest). But June is as tall as him, but although she is tall she is small.
- It's been said that Leo may have a crush on June and vice versa, but not much evidence has been presented to support this.
- In the episode "Ring Around the Planet", After Leo got Saturn's ring back home, June walked to him and gave him a big hug; you can see Leo smiling because of the hug. Since good friends hug each other all the time, this is not too much in indicating a crush.
- June was always the one to comfort Leo when he gets sad, and he has greatly appreciated it.
- In turn, Leo comforted June when she was feeling down.
- In "The Glass Slipper Ball", Leo complimented on June's dancing skills and told her she was the best dancer he knew. This comment made June blush and she can't stop smiling. Leo also complimented on June's dress that she wore to the ball, which also made June blush. Although this may seem a little bit crush-like, it’s more said and done in a friendly, non-flirtatious manner.
- In "Rocket's Firebird Rescue", Leo was granted Music Power and may have it permanently.
- In "A Galactic Goodnight", Leo says that he uses his baton as a nightlight every night, which helps him fall asleep.
- In the episode "The Christmas Wish", Leo's wish was a new baton head.
- He is the only character on Little Einsteins revealed to have a full name: Leonardo.
- He prefers his friends to call him Leo.