Weirdly enough, the Netflix order for "Just For Sidekicks" is different from the broadcast order. Unfortunately this partially takes away from the neat experiment that was executed with this and "Games Ponies Play". We'll get to that in the latter's review.
In any case "Just For Sidekicks" is still a very fun episode with some good character development for Spike. The latter point is particularly interesting, as I didn't notice this character development when I first watched the episode. Spike episodes always contain some character development, and Spike is a character that's rife with opportunity for such. Having learned much less in life than the mane six, he can learn things that they already know but which haven't been addressed in the show. This episode sticks to the formula of "Spike acts like jerk, Spike learns lesson", but the typically great execution keeps it from being even close to wearing thin.
Another reversal of opinion I had was regarding the Cutie Mark Crusaders. While at first I thought they became a little irritating, I found them quite charming this time around. Their obsession with cutie marks is utilized more than their last few appearances, but is again much better executed than it ever was in season 1. It's much more a background motivation, which allows for much more fun to be had with it as simple comedic relief from a main story.
The main plot is fun as well. Spike looking after the animals provides the episode with some great comedic moments, and the ensuing shenanigans are quite entertaining. The lesson at the end results in a touching moment between Spike and the animals, which is a stand-out scene of the season. I find Winona, Applejack's dog, to be particularly adorable, though most of the animals are cute in their own way.
So, yeah. Even with the compromised episode order, "Just For Sidekicks" is a fun episode with great character development, and the glimpses of the other episode happening at the same time are an intriguing experiment. I'll discuss that when I review "Games Ponies Play", but "Just For Sidekicks" is a great stand-alone episode. S3 hasn't left its stride yet.