How should I explain my son's autism to his 3-5 year old friends?

Hello

I took my 4 year old son with autism to an NT birthday party today, and it was clear to me that the kids did not understand his behaviour (i.e. not conforming and problems transitioning). Some laughed at him and some were nasty.  Does anybody know of a youtube video or short animated story teaching young NT kids about autism?  I believe the kids and parents could benefit from some information. I'd be so grateful for some recommendations.

Thanks