It is super acceptable for the bride and groom to get the first pieces long before others, but strange for just the king before the queen. If I'm writing this story and I put it in the pie, I'm also killing Margaery, because it took at least a minute for the poison to act, and it would be super normal for the bride to also get pie in that time. Not to mention that others had pie on their forks, moving towards their mouths. The hole is that this means that the queen was left out of the equation. Margaery not dying *can* be explained by Joffrey being an asshole and just scarfing down pie while even the bride chills. If that's the case, however, it creates a different hole in that nobody else, who had been served pie and would be expected to eat while Joff was munching and batting around Tyrion, died

Regardless, I'm now guessing it was Baelish, and I'm just going to accept the holes because they're not the most meaningful things. They only matter in an attempt to Sherlock Holmes it