One card costs $15, two cards cost $25, five cards cost $55 and 10 cards cost $105. Shipping is included in those costs if you live in the United States. The brothers have several pro tips for buyers.

She can’t stop dancing to the funny tune inside her birthday card. — -- They say the best gifts come in small packages, and it seems this baby would have to agree. Take a look at adorable ...

The cards (still available for a pledge of $15/£10 online) are delivered in ‘safe mode’, which means you can start and stop the ‘jaunty’ happy birthday tune as much as you like.