Is it rude to tell the ice cream man in Istanbul not to mess with me?

Simple

You don't buy it

Let's just analyse this for a bit shall we? You're not paying for the ice cream, you're paying for the experience. If you like ice cream but don't like entertainment or 'street entertainment' to be specific, buy your ice cream from somewhere that doesn't do that... Do not try and get the ice cream vendor to not 'do his show' for you... That is very rude. You buy from him, you are pretty much buying into the act and to turn around and say, "Please don't do that." is like asking for something and then refusing it.

This reminds me of Singapore and the icecream and bread sandwiches they sell. I know several people that would turn it down because of how 'boring' or 'weird' it sounds, but the fact that I bought one without expecting anything made the experience that much better. Ice cream and bread? it works!

The fact that you are going to get upset because he's trying to entertain you means you should not be buying ice cream from street vendors. If it is that detrimental to your trip, just buy ice cream from places that don't serve them with large long spoons.

Having visited Istanbul and gotten Dondurma from such a vendor complete with the show, all I can say is it was one of the funnest experiences of the trip.

I had no idea about what went on when asking for an ice cream cone and the Turks who were around when it occurred were all obviously in on the joke since they grew up with it. The showmanship alone was worth the price of the cone, but the ice cream was very good too.

If I had children I'd certainly want them to experience it, afterward I asked the vendor to take a picture with me, which he kindly obliged. I can't find it right now, or I'd post it as an attachment.

My unsolicited advice? Even if you won't enjoy it, allow your children to do so, they'll be delighted by the show and definitely enjoy the results.

Just practice your eye-hand coordination, e.g. you can play catch with your kids. If your eye-hand coordination is good enough and you have fast enough reflexes, you'll be able to snatch that huge bulk of ice cream enough for 20 persons that the ice cream man was holding in front of the woman's face in the video.

Other answers have pretty much exhaustively answered the moral part of the question. But if you really need to annoy the ice cream man, you can:

• Play the same game with him when it's your turn to give him the money. People nearby will enjoy it as mush as they enjoyed watching him fooling you.

• Or you can try to imitate an average annoyed Turk by saying something in Turkish (yes it's hard), like e.g.:

"Abicim hay?rl? i?ler, insan gibi bi dondurma yemek istiyorum, lütfen zehir etmeyelim."

Which roughly means:

Good deeds, my lovely brother, I just want to eat ice cream like a normal person, let's not ruin it for me.