Giddy up!

Kourtney Kardashian and Scott Disick's son Mason Disick turned 2 on December 14, and for his big day, his city-slickin' family took things to the Wild Wild West.

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Proud grandparents Kris and Bruce Jenner pulled out all the stops for their grandson's fete and hosted a cowboy-themed birthday party at their Hidden Hills, Calif. home complete with a petting zoo, pony rides and an arts and crafts table.

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Mom Kourtney, 32, who's pregnant with her and boyfriend Scott's second child, helped her first-born son blow out the two candles on his 10 gallon hat birthday cake.

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Also in attendance: Mason's aunts Kendall, 16, and Kylie Jenner, 14, and uncle Rob Kardashian, 24.

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