
If you're looking for anime similar to 21 Emon Uchuu e Irasshai!, you might like these titles.
The space travelling company, YAT, is thrown into the unknown realms of the outer space. At the same time, the group encounters the psychic, Maron, and scientist, Note. Subsequently, the two of them are attacked by the evil monarch, Ganon. Note was captured and taken away after suffering an attack from one of Ganon's followers, Baras. In order to rescue Note, the group had to use the instantenoeous portable machine which Note invented so as to travel to Ganon's planet. However, no one knows where the planet is...
In the future, a dimensional tunnel in space allows people to travel almost anywhere in the universe aboard spaceships. Many travel companies take advantage of the situation and offer tours to faraway planets, such as the Yamamoto Anshin Travel company (YAT for short). Staffed by its captain Yamamoto, his daughter Katsura, mascot Bukki, robot Kanabi and others, YAT is soon joined by Goro, a boy who’s been searching for his missing father for some time.
Sorao is an ordinary student who lives an ordinary everyday life of a typical kid, accidentally makes friends with two aliens stranded here on Earth. His life changes as he decides to help them find a way to get home.
Dr. Keida has successfully invented a time machine called Time Bokan, and to prove to his lab assistants that it works, he uses himself as the guinea pig. The test run was a success as it traveled through time and space within a matter of minutes, but when the device returns the lab assistants are surprised to discover that the doctor is missing, and only a talking parrot and a diamond are found...