I am looking to get this for someone but I forgot the name of the effect as I bought it quite sometime back.
It is somewhat like a brainwave/invisble deck, but you start by showing a pack of totally blank cards. You concentrate hard and a card appears but it only has the front printed. The back is blank. Then you concentrate on the back... and this time, a card with the bicycle back is printed. When you really concentrate again and picture the whole deck, suddenly, every card in the deck becomes printed. However, it is taxing on your mind, and the moment you stop thinking, the whole deck going back to being blank on both sides.
Bingo!
Thanks. That is the one.