Luggaa wasn't actually born... She started out as, not a tadpole, but a robot. So she isn't supposed to be real and couldn't even be here if one little thing had changed in Keroro's invasion "plans".

I'll make the long story short. Basically Keroro started to want a girlfriend (Tamama was enraged when he found out) and since any girl wouldn't like him, he got greedy and had Kululu make a robot one. Kululu decided to be a jerk and have Luggaa like someone else instead of Keroro to tick him off.

When Keroro figured this out, he had a plan and it would either destroy them 或者 get rid of Luggaa....