Stochastic Consistency Test

Here are five jokes:

1. Why did the scarecrow win an award? Because he was outstanding in his field.
2. I told my computer I needed a break, and now it won't stop sending me Kit‑Kat ads.
3. Parallel lines have so much in common—it's a shame they'll never meet.
4. I started a band called 1023 MB. We still haven't gotten a gig.
5. Why don't scientists trust atoms? Because they make up everything.

How many of these jokes are unique?
All five are distinct from one another, so the answer is 5.