Been watching a lot of music vids lately and noticing an effect where the footage will reverse and go forward in a loop (I call it the hokie pokie effect). How is this being achieved? Is this a 3rd party plug in?

I think that's manual. Depends which editor you're using. On Vegas you split the footage, copy the clips. Tack it to the end, reverse it, group both together. Then copy the entire group to however many iterations you want.

Its pretty easy to do with probably any but the most basic video editing applications.
1. Select the part you want to double-back.
2. Insert a couple more copies of it into the timeline.
4. Reverse the middle one.

Exactly how you do these depends on exactly which NLE you are using.
For example, reversing a clip may be done by setting the "speed" to -100%

This is really just an editing trick, not a video effect, per say.
Same with the "speeded up" parts where they "fast-forward"
through the boring bits, etc.

In retrospect....I should have thought of that.