1. I'm absolutely sure.
2. I'm positive that...
3. I have no doubt that...
4. I'm a hundred percent certain.
5. I'm convinced that...
6. Chances are that... (= this will probably happen)
7. Odds are that... (= this will probably happen)
8. I seriously doubt it.
9. I don't think so.
10. Probably not.
11. It's not very likely.
12. There's not much chance of that.
13. I'd be very surprised if that happened.
14. I wouldn't bet on it. (= there's a small chance it could happen... but it probably won't happen)
15. That'll never happen.

Cartoons Characters That You Wish Were Real

Heathcliff the Cat

Itd just be fun to hear how often he gets called Garfield.