Alejo is a human boy and one of Astro's friends. His Japanese name is Tamao. He is almost always seen wearing a large hat, so it is not known what the color of his hair is; however, in the episode Eternal Boy, he is shown with his hat off, showing his short gray hair. Alejo is a science geek.
- Lara Jill Miller in the USA version
- Motoko Kumai in the Japan version