From the History Notes range by Cath Tate, these cards are both educational and witty, making them ideal to send to wish a friend happy birthday.
Depicting a historical figure on the front, the back cover of the card features a brief biography of the notable person. Here's Einstein to wish you a relatively happy birthday - he's funny AND brainy.
Blank inside for your own message, each card measures 12cm x 17cm and comes with a white envelope.