"Baby Cakes" opens with a large amount of pure adorableness, showing a harmonious situation involving the Cakes' newly born babies. This doesn't last, and the babies' appeal starts to go away. Thankfully, the episode certainly makes up for it with some madcap charm courtesy of everyone's favourite party pony.
Pinkie carries this episode, being a consistently entertaining presence throughout. While a happy Pinkie is still more pleasant than anything, a grumpy Pinkie can be almost as funny, and certainly is here. Her increasing frustration is communicated in a typically offbeat way, and it's very amusing. However, she also experiences some notable character development, in realizing that some things require a more serious outlook.
Indeed, in this I think is the better message. Things are often harder work than may be expected, and Pinkie realizing that is an excellent character moment. And the fact that Pinkie is able to adapt to that provides a far more excellent theme than the lesson itself. Earlier on it's stated that some people just aren't cut out for responsibility, but Pinkie's learning of the lesson shows that people can learn responsibility, which I think is a very strong message.
The babies are a little bit obnoxious, but they're supposed to be. Pinkie's irritation is relatable and understandable here, which makes her more sympathetic. That does become a bit of a problem when at times when it seems Pinkie's supposed to come off badly, and I don't think she's given enough credit for the effort she does put in. As a side note, final scene where the Cake babies say Pinkie's name as their first words does seem to be trying a bit too hard, and falls flat.
This is yet another great episode with a lot to offer both thematically and in terms of character development. At this point, S2 is a stronger season than S1, and while its failures are worse than S1's, its successes are much better and more frequent than those of the first season as well. This episode may not be the absolute pinnacle of the season, but it's an excellent addition to the show.