In an AMV I'm making right now, one character loses everything near the end of the series, and I wanted to evoke that sense of "loss" by playing clips of her past times with her friends by having the main clip transparent while the clips from earlier in the series (the "memories" ) play simultaneously.
I hope this makes some sense. The only example I can think of that mirrors this effect or comes close to it is here right around 1:52 - https://www.youtube.com/watch?v=dcSWlET_qpI
A similar effect. Hope this all made some sense.