Jasper Kuipers made a video for Micropia, the museum of microbes in Amsterdam, depicting a scenario for the evolution of multicellularity and, eventually, Volvox. Unfortunately, I can’t embed the video, but you can check it out at vimeo.com/groups/18713/videos/121359995.
It’s a beautiful animation, showing a plausible scenario for predation as a selective pressure driving an increase in size. I do have a couple of very minor nits to pick (flagella are shown beating anti-parallel and out of sync when they should be parallel and in sync; reproductive cells are labeled ‘sex cell[s],’ but the life cycle depicted is the asexual phase), but it’s still a lovely video.
The Volvox meetings have usually (well, all four times) had an art contest; I think this would be a shoo-in for Animated Shorts at the 2019 meeting in Tokyo.