Colleen and I have been doing these “ball pass planks” the last few days, only we’ve been rolling a softball back and forth. Technically it makes the planks that much harder to do, but also more fun. (Not hard to raise the fun factor, as doing a regular plank is zero on the fun scale, in my opinion!)
Like the kids in this video, we’ve been aiming for 30 passes. We have yet to get there before messing up. But the main thing is, we’re getting ourselves to do planks every single day. It’s a lot easier to say, “Let’s see if we can beat our current high in ‘plank ball’ ” than to nag each other about doing an exercise neither of us likes.
90in9 
Anything to make it fun! That’s a pretty good idea.
Probably devised by some genius of a PE teacher. Works for us!