I remember when I was 11 years old and got to the final castle in SMB3 for the first time. I was so excited, and so nervous. So nervous, in fact, that I literally tiptoed over each square, terrified of what might be coming. As it turns out, tip-toeing is not the best strategy.
Somehow, though, I was able to avoid instant death. I just wish there were more surprises like this throughout the game.
Death By Troggles 
Those literally made me jump the first time I encountered them! The loud noise that accompanies them doesn’t help either!
Same.
I do wish the hit detection was a little more ruthless for these. You’re at the last level, for crying out loud, time to take off the training wheels.
I do wish that they had gone full measure for the 8th world. I mean, sure, the difficulty ramps way, way up from the fairly easy game that surrounds it, but after 8-2 and the castle, I was excited/terrified for the rest of the world. Turns out I’d already passed the hardest levels of the game (and, since beating the castle opens the lock, you don’t have to replay them, even if you should game over on the last few levels.
In my opinion, there should have been a couple more standard levels, with blazing hot difficulty. Kaizo traps, false blocks everywhere. Make it hurt.
Yeah, man. I remember 8-2 being crushing and thinking I had no chance to do the rest after I passed it.
I’ve played this one to the end so few times I forget about those guys. I think I was warned about them as I was about to scroll to them, which killed the impact.