During the month of March, accumulate 10,000 total double unders. If you're feeling really ambitious and already have competency in double unders aim to complete all 10,000 yourself. FYI, that breaks down to about 322 per day for 31 days. Not too bad if you're decent at double unders.
If you're like me and completely suck at them, the other option is to partner up with one or two other people and do this as a team challenge. You can divide the total reps amongst the team and make the total number a little bit more realistic and manageable.
Let me know if you're taking part. And good luck if you're up to the challenge.
Carl Paoli breaks down the double under progression.