(1) Print 1 copy for each student. Stick the worksheets to the classroom walls.
(2) Students choose 1 worksheet and start filling in the gaps with their ideas.
(3) In 1-2 minutes the teacher gives students a sign (e.g. rings a bell) and they go to the next worksheet.
(4) They keep going like this until there are no more gaps left.
(5) Everyone returns to their original worksheet and reads the letter out loud. It is always very funny.
POSSIBLE FOLLOW-UP:
Suggest writing a real letter to Santa. It can be then packed into an envelope and sent to Santa's Office for real.