I can't remember exactly when, but I've been developing elearning multimedia since 2001, and up until about 2017 we were building everything in Flash, so stuff like this always grabbed me and my co-workers attention. The co-worker who showed me this hasn't worked with us since about 2007 or 8, so before then for sure. He was a younger fellow who practically lived on newgrounds and albinoblacksheep and other such sites...

Yeah this one really stuck in my memories. The art was so cool. Remember Ninjai,the little ninja? That series was soo well done, but unfortunately seems to have disappeared from the internet. I'd love to go back and re-watch them...