McDonald's is bringing back its classic Shamrock Shake to celebrate St. Patrick's Day.  The minty Shamrock, a short-time fixture at the Golden Arches since it was introduced in 1970, returned Wednesday and will become as rare as a four leaf clover after St. Patrick's Day, March 17.

In a high tech touch, McDonald's is introducing an official Shamrock Shake Finder app for smartphones.

The Shamrock brings in the green, as in money.  McDonald's definitely gets a profitable sales boost, especially between now and March, when everyone wants to be Irish.  Here's more from USA Today.