That one episode that everyone hates but I actually like.
I don't think there's any episode where I differ from the consensus quite so much as I do this one. As far as season 3 goes, there's two consensuses: Everyone loves "Sleepless in Ponyville", and everyone hates "Spike At Your Service". Everyone, that is, except me. I actually like "Spike At Your Service"... though, I'll admit that it's not perfect.
At the centre of most Spike episodes is Spike himself. This episode differs from the usual "Spike acts like a jerk, then learns a lesson" formula, though it does so to the extent that it almost makes Spike feel out-of-character. Spike's usually shown being fairly selfish, yet in this episode he acts with some sort of honour-bound altruism. It almost seems out of place in regards to dragon code, as before we've seen dragons to typically be greedy and selfish.
There's something in the way of character development, but it's Spike growing out of a character fault that was invented for this episode, so the character development doesn't have much impact. Usually, character development is based on something that will make the character grow as a person, and result in changes for the rest of the story. Here, removing the manufactured character fault simply brings us back to square one, as beforehand there was no reason to care about Spike's dragon code that we'd never heard of before.
Consequently, the writing is somewhat poor. There's a few other small bits that certainly don't work, such as Twilight screaming and running from the Timberwolves, but altogether the writing isn't very good. Except when it is. While the story itself is bad, the episode boasts some of the best dialogue the show has to offer. Whenever Spike's not involved in conversation, dialogue is clever, funny, and oh so natural. It's such an odd thing. Conversations between the mane six are so organic in this episode that it almost offsets the weak main plot.
And the episode's actually rather fun on top of that. It keeps a nice pace, the shenanigans are entertainingly silly, and every character but Spike and Twilight are written really well. The introduction of the Timberwolves is interesting, and their cel-shaded animation is gorgeous, though it clashes heavily with the simpler flash animation of the rest of the show. The Timberwolves look out of place, which is unfortunate because they are so gorgeous on their own.
Okay, maybe I do get why most people don't like this episode, yet I can't help but enjoy it. I'm not sure if I can even acknowledge it as good, yet every time I watch it I find myself having fun. There's something in the dialogue of this episode in particular that makes me particularly happy, and aside from that I still find it to be a fairly enjoyable episode, despite just how flawed it is.