For teachers who've seen this with me, this was the activity called 'Tommy's game' - it's his favourite. You don't have to use a puppet for this, or even a sheet...a piece of cardboard will do, but the theatricality of the cloth and Tommy makes the activity a lot more fun and interesting to play.
I like this a lot as you don't have to rearrange the seats in the classroom, it's easy to play in the space /aisles between the tables.
Students sit in two lines with the curtain between them. You sit holding your puppet and one end of the curtain and another student does the same (see the pictures below) Put a pile of flashcards face down at the front to the line. The students at the front of each line pick up a flash card each and hide it behind the curtain, all the class call out '3,2,1' the curtain is dropped and the first student to shout out what he/she sees on the other student's flashcard gets the point. Alternative. Using show me boards and to make it more difficult, ask the students to write things such as the first letter of a month/last letter of a month/simple maths/a two digit number etc.