Maybe not quite what you meant but...
I do a writing exercise where I ask the kids to write a description on how to make a peanut butter and jelly sandwich. Then I bring out a jar of jelly, peanut butter, knife, and bread. I make the sandwiches following their directions EXACTLY and then hand it to them to eat. My favorites are when they say things like 'put the jelly on the bread' and then I place the jar on the bread. There's always one that says something like "slap the two pieces together"...

Fun way to get across the point that details matter.
I always have to swear the class into secrecy to not tell younger students - spoils the fun for the next class.