Fancy!
Check out the above video to see some slick moves at the 0:50 mark. You know that end-of-level trick where you can trap a turtle on a single stair step to get a bunch of 1UPs? The maker of this video has some smooth moves that creates that same opportunity in World 1-2, a fair bit earlier than the usual World 3 trick.
And I guess I never really thought about it, but Japanese YouTube user Haya S shows that you could really do the same thing a bit later on in 1-2.