via esquareda:

“Small is Tall” - great edit job.

Super-funny. It never made a ton of sense to me either. From the producer:

Things I’ve learned from comments:
Grande=’Big’ in Spanish & Portuguese
Venti=’20’ in Italian

Sizes used to be:
Short (8oz), Tall (12oz) and Grande (16oz)
Then they introduced the 20 oz cup and called it Venti, 
So the Short (8oz) became the kids size
(still available when asked)

So… Their Short is the kids size, Tall is their ‘small’ size, Grande is their ‘meduim/regular’ size and venti is ‘supersized’ and will make your brain explode ;)

Source: esquareda