This simple but fabulous mentalism effect in an impromptu format can be performed in many different ways.
The magician takes a notepad and writes a cross with a pen dividing the first page into 4 boxes. A spectator is asked if he knows the four Beatles' names and you explain that in those boxes you will write their names. The spectator mentions their names ones by one, and you write them on the pad one at a time.
After writing 3 names, the magician explains that it will be impossible to write the fourth Beatle's name because the first page has the lower right corner missing.
Astonishingly, he produces from his pocket the missing corner and this one has the image of the Beatle who was not mentioned, drawn on it. He gives it to the spectator as a souvenir. The spectator checks that the little piece matches the torn page perfectly!
Easy to do.
The spectator mentions where to write each name.
Give everything as a souvenir.
Perform it with the four Aces, the four seasons, the four elements, products for the company you are working for, etc.
Includes replacement and a file to print your own pages.