Pi is an impossible memory effect. You show a small book in which the decimals of Pi are listed, and explain that you memorized it. The spectator opens the book at any page, tells you the page number, and you can tell him the first digits of the page!
Then you ask him to tell you a sequence of 5 digits, anywhere on any page. Starting from there, you start reciting the decimals of Pi! Actually, you recite so many decimals that the spectator has to turn pages to follow you!
Finally, you ask the spectator's birthday, for example 14th of July. You then reveal the page, the line, and the position on the line where the sequence 1407 can be found in the book!
No stooge
No preshow
No peek
No crib