I think it is possible but not very probable. Lots of live interviews held with him and some of them were in the early stages of machine learning, so a machine could not answer the impromptu questions, let alone making jokes about them. Here is my post about him as a farewell tribute: https://steemit.com/science/@ecotone/you-are-the-center-of-the-universe-confirmed-by-stephen-hawking-evrenin-merkezi-sensin