Detective Haika

An alien named Keroro from pekopon planet who's trying to invade the earth, come to the earth with his 4 other members that are Giroro, Tamama, Kururu, and Dororo. With the 5 of them together, they're called Keroro Platoon. Their mission to invade the earth never happen, due to their care for humans since they come to the earth. 

Keroro care for Fuyuki Hinata (Best friend), Giroro care for Natsumi Hinata (Giroro's crush), Tamama care for Fuyuki's friend called Momoka Nishizawa (bipolar insanity), who happens to have a crush on Fuyuki, Kururu care for Saburo Mutsumi (who discovered Kururu, and both are genius), even though he doesn't seem like he care about Saburo though, and Saburo Mutsumi is Natsumi Hinata's crush, last but not least is Dororo. I did NOT forget him, did I? Dororo care for Koyuki Azumaya (Ninja friend), Koyuki is Natsumi's best friend who often get close to to her and make Giroro jealous.  

And there's also Angol Mois. When Mois is still young, she always play with Keroro, therefore she fell in love with him. Thus, she got hated by Tamama. I don't know why, but Kururu scared of her. Fuyuki and Natsumi's mom called Aki Hinata. There are also stories about Keroro, Giroro and Dororo's past when they play together. The 3 of them are best friends. This anime is very funny, go watch it! This anime have a manga and Nintendo DS game too! It was all entertaining! Thinking about invade I suddenly remember Shinryaku! Ika Musume.

You don't know what "friend" mean? Speaking about friends... They are people who you quarrel with and not able to see sometimes. They are lively... And they are good people. People who will be there for you when you need them most. And they do their best to remind you of that purpose when you forget it.
~Keroro Gunso