So you can tell them apart from blueberries!
Basically you just give a charity some money and don't tell anyone about it.
2...and don't ask me how they got in there. (My 87 year old grandma just told me this one)
Because they always blow their trunks off!
Because they've no pockets to put things in!
A blueberry
So you don't get them confused with blueberries.