If you're looking for manga similar to Keroro Gunsou Movie 2: Shinkai no Princess de Arimasu!, you might like these titles.
Vintage 70's manga from Yasumi Yoshizawa follows a young middle schooler named Hiroshi. He's running around one day, when he accidentally slips and squashes a wide-eyed frog onto his shirt. To his surprise, Pyonkichi the frog is still alive and can speak to him! It's time for some fun adventures for Hiroshi and Pyonkichi!
"There’s an old man with a face like a frog living in my house…what’s up with that?" A short comedy about what happens when an elementary school student who looks good in short pants and a middle-aged amphibian live together!
Shibata Youichi is an ordinary high schooler, but one day he runs into a mysterious heroine! The cute girl knows his name, and (as in a stereotypical anime) she's an alien who needs him to help save her people! Soon enough, Youichi finds out that this situation was too good to be true... The girl, named Kyara, does represent aliens, but her people are actually interested in Japanese manga/anime/game culture. They want to use his home as a base and his brain as a measuring tool of the level of appeal of their heroines!
The story centers on an "evil corps" led by Don that is planning to conquer the universe. The group sets out to invade Earth, but their spaceship disappears. They encounter an earthling boy who helps them. The aliens take up part-time jobs and continue with their plans to conquer Earth.
Tsutsui Yukitaka is a freshman entering high school who hopes to become a good baseball player. However, when he walks into his new apartment, there is a man in the room who claims that he is an alien who lost his memory. He is in fact the first prince of Planet Dogra, known to have the best brain but the worst nature.
On his way home from school, the shy young boy Tecchin finds the body of a young girl lying in the street. He alerts the police, only to come back to find she has been replaced with a life-sized doll. Tecchin takes the doll home and repairs it. She comes to life and tells him that they are both Grand Dolls, alien beings bent on world domination.