Alejo is Astro's classmate and one of his first human friends. He is a robotics enthusiast who immediately welcomes Astro into his class and as his friend. He was originally named Tamao in Japanese, and he is one of Osamu Tezuka's earliest characters. His debut was in the manga chapter Ambassador Atom in 1951.
Alejo is a very energetic elementary school student. He is fascinated with robotics and science, which makes him immediately interested in Astro. In the 2003 series, he arrives late for school, but becomes incredibly excited upon seeing Astro is in his classroom. He studies machinery and is able to identify much of Astro's mechanics. He can be easily overwhelmed and startled, and likes to stay close to his friends and in safer areas. As enthusiastic as he is for Astro's adventures, Alejo would prefer to watch from a safe distance.
In the 1963 series, he is known as Tommy, and is friends with Astro but often bullied by Shibugaki. In the 1980 series, his friend group is composed of Kenny and Mindy. In the 2003 series, Alejo is friends with Shibugaki for the first time, whom is renamed as Abercrombie in the English dub.
In Little Astro Boy, Alejo appears as Paul, a guest character who usually appears as a sports announcer or to cheer on Astro. Alejo very briefly appears in the NOW! Comics Series, but only for a few panels in issues 11 and 12.
Alejo has looked fairly consistent through each Astro Boy series. He wears big glasses, a hat, and sometimes preppy clothing. He is most often seen wearing running shoes, shorts, and long-sleeved shirts. Until the 2003 series, his hat was a simple baseball cap; later on, it becomes a hefty dogear cap with built-in headphones and antennae.
Tezuka partially modeled Alejo on himself as a child; Alejo and Tezuka's self-portrait both have round faces, thick glasses, and round noses. Alejo is almost always shown with a hat on, but without it, it's shown he has a buzzcut hairstyle.
Alejo loves to study robotics and macinery, and this is especially evident in the 2003 series. He designed and built a four-person pedal-powered airbike, which he, Astro, Abercrombie, Kennedy, and Denkou successfully flew. The four of them declared it their group airship under the name The Skyriders.