What movie is that where a little boy rides his bed, i think to a land. And a train chases him at the end?

Well, I remeber this as a cartoon. and the littl eboy is sleeping. and his bed or a blimp comes and takes him to a dreamland. and theres a guy. well i remeber one part where a lady sings and gets him all dressed up to meet a princess. and he doesn't like her at first. but the princess plays a harp. and at the end hes in a dark cavern and some black goo comes and atacks the king guy wh rides the miny trains? and the gold septar thing gets taken and he has some whacke p weird friends? i dunno. i know for sure this was a real movie, with a flying bed lol. so please help. or this is going to bother me for the rest of my life until i find out.