I told this in my greek class and the teacher said I should be taken out and shot!

Tupte tupte
Ara tis ekei
Dianaros
Dianaros tis
Dianaros kai Supremes

(I did try to type this up in Greek but I can't)

I haven't heard this before, and I can't understand it. Would you please explain it for us?

It's a Greek "knock knock" joke.
knock, knock.
Who's there.
Dianaros (read Diana Ross)
Dianaros who
Dianaros (Diana Ross) and the Supremes.

Well i did warn that it was terrible.

Your teacher is so kind; you should be tortured for several days and then shot! However, notice the word "typte" that you used. Good or bad the 'joke' can not be understood, because "typte" can not really be compared with "knock" in this case. Even the pronunciation of "knock" bears a similarity with knocking at a door, while "typte" is purely an imperative verb. When I hear the word typte I understand "you must beat", nothing like "knock knock". Perhaps you should use the indicative form "typto", which, even as a sound, comes closer to the meaning of the joke.

Then you could play with the name of Diana (Artemis) and say just "Diana", and after the response "Diana who", you could say Diana Ross and the Supremes.

I knew that I'd seen the word "knock" somewhere, and it's kopte, imperative of koptore.

That makes the joke a million times better ;-)

You are right about the imperative, but "koptore" does not exist, the infinitive is koptein. Again, you wouldn't use the imperative, but the first person of the indicative, i.e. "kopto".