Bad to the Phone is a short for Foster's Home for Imaginary Friends.
Bloo is put in charge of making a recording for the Foster's home phone. At first he is seen bored when he does it, but soon becomes bent on getting the recorded message just right.
He also gets the help of the other imaginary friends to help in perfecting the message, as well as asking Goo.
Although, soon enough, he becomes satisfied with a recording and gets it saved, however, Madame Foster has so many plugs plugged into the same socket, causing the phone to get overloaded where Bloo gets annoyed with it.