Before the exams happened I had my students working in groups and writing limericks. It's pretty simple to explain to them. A five line poem where the first, second, and fifth lines rhyme with each other and lines three and four also rhyme with each other.
There once was a teacher named Zach. A
Eating too much kimchi made him go wiggity-wack A
He went crazy and couldn't teach anymore B
Looking after him became quite the chore B
So one day the school shipped him in a box to Iraq A
I had the first grades work in groups of four. It usually took them around 15/20 minutes to get it right (and to revise). the second graders I had working in groups of two and they usually took around 10 minutes at the most. I had each group put their limerick on the board and they were read as a class. The best three lyrics got their group candy as prizes.