You've inspired me to make something like that. Simple but very cool and effective

Watermelon shot. Now you see it...Now you don't

Do the people who make these insane cannons create them from their own imagination? or do they modify things that they have seen before and thought would be successful. Just wanted to know as i have just started to make cannons, or a cannon, and it took me no time as it is far to basic for my liking.