Rope tricks can be really cool once you know how to do them. My problem is, the instructions I find for rope tricks in the Bear Handbook and the Cub Scout Magic book seem to be edited by a person who didn't understand how to do the knots correctly. On some steps I found that I had to do the opposite of what the instructions told me and other steps were completely left out.
For instance: on the Man Overboard knot, the Handbook says to make loops but it neglects to tell you that ever other loop has to be reversed. The Cub Magic book explains it better. This video helped me figure that out.
The Cub Magic book describes this trick as the "It's not" knot and in the instructions, it mixes up from which side of the loops you put the end of the rope. In this video, it's called the Chefalo trick. Basically, you're tying a loose square knot and depending on which end you pick for the last step will determine if you insert the end from your side or from the back side.
Here's the Chefalo with a ring added to it.
Of course plenty of practice will help a rope trick look better. If you have to go slow and think through every step as you perform it, the boys will figure out what's supposed to happen and you'll hear about it if it doesn't work. You really have to learn the trick well so you don't have to think about the steps as you do it - just like how you tie your shoes now. You don't think about tying your shoes anymore, you just do it. When you get the rope trick down like that, you do it fast enough that most people can't follow what you're doing when they see it the first time.