I think the joke may have lost something bearing in mind the language barrier but the Dalai Lama tries to understand the joke

Karl Stefanovic, an Australian newscaster, was given an interview with the Dalai Lama. So he decided to tell the Dalai Lama a Buddhism joke, well why not? It's quite a good joke but I not think easily understandable by someone whose first language is not English and who also may not be a regular pizza eater...

"theoretically possible"