Milk-chan is a girl who lives in a house stuck on the side of a building with her two sidekicks: Tetsu-ko, a paranoid robot that looks like a bottle and Hanage, a green blob with a moustache. 
Milk is poor and she can`t pay the rent, especially after her attempt to extort a local ant family fails. However, she is saved because the president himself offers her a job (some sort of a secret mission). Milk-chan answers the phone to receive missions from The President by saying something like "Hello, Bank of Hokkaido. Just kidding!". 
After getting her mission, Milk-chan and her sidekicks take off aboard the "Milk-6" helicopter to go on her mission. Did I tell you this is a spoof of 1970s spy thrillers or some sort of Bond movies? :) 
(Source: AniDB)