answer:Hello, Dolly! was produced by Chenault Productions and distributed by Twentieth Century-Fox. Disney does not have any connection with the work. I’m assuming that the clip they used was short – I haven’t seen Wall•E yet, it comes out here later than the US – but if it was then it may well have constituted fair use, especially if they attributed it in the credits. They likely sought permission beforehand. For more information on copyright fair use in the US, see this document from the Copyright Office. PS: Interesting video.