According to Jim Recap: Birthday Boys
As Kyle celebrates his first birthday, Andy celebrates his birthday too (some birthday). Unfortunately he isn't as good a sport about sharing birthdays as Kyle is, so he demands to be taken out for a 72-ounce steak. Jim is only too happy to comply, but first he has to find his "steak pants", which will provide him enough room after eating four-and-a-half pounds of meat in one sitting.
To his dismay, Cheryl wants him to pay for the dinner because Dana has been buying so many things for the kids (and she's spending a lot of money on the gifts). But he agrees to do so, though when he actually sees the bill, he has a momentary relapse. He does eventually pay for the meal, and he gets his 72 ounces (Andy does too, for a whopping 144 ounces between the two of them).
Later, Dana brings a rather lavish gift to Kyle - a mural for his room, that apparently cost $500. To try and show her up, and show everyone that he's somehow better than Dana, Jim buys the girls a pony. Well, it's not really a pony - it's a donkey. But they think it's a pony, and it was a lot cheaper than a real pony, and that's all that counts. At least, until it destroys Dana's mural, which was in the garage, it is. Then Cheryl isn't too happy, and Dana isn't happy either.
But at least that brings everyone together when they talk about the real feelings behind it all. Jim doesn't mind Dana spending the money, he just doesn't like it when she tells everyone that she makes more money than he does right out in the open like that. That makes him feel bad. Not that he'd ever admit it or anything, but it does. No word on what they are going to do with the "pony".
