I divided the sentences in the lyrics, so they had to find the other half of their sentence, the first part was on red cards and the second on green. That meant they had to get up, walk around the classroom, and find their other half.
RED:Remember when we were young,
GREEN:playing cops and robbers in our underpants
Sorry, I forgot to post that activity, and I don't have it any more but it's really simple to make yourself. I'm happy you found it, even my parents' class loved this lesson.