This is a pretty crazy video, but it's something me and my cousin discovered by complete accident while messing around on my server, so we decided to fraps it.
I have only seen two videos that have to do anything with this, and they are both quite different from this one.
This effect is acheived by doing .cheat casttime, then spamming the booterang at either yourself or someone else whose moving very fast (on mount or mod speed). This makes the boots build up beacause they chase their target, yet never reach it.

*If you think it's choppy, thats just cause im .appearing to my cousin over and over again..