We've got all the inside details and an unbearably cute gallery from the over-the-top Wild West-themed party after the jump...
Hosted by grandparents Kris Jenner and Bruce Jenner at their Hidden Hills, Calif. home, Mason's bash celebrated the day in style—complete with a full-on petting zoo and an enormous cowboy-hat birthday cake!
We can't imagine what year three will bring, not to mention baby No. two's arrival! But if it's as much crazy cuteness as this, we can't wait.