I feel that this episode deserves more comments-
First of all, the animation of this episode was very, very good. I'm guessing Iwane was a Key Animator, as Natsume isn't this good. The "two-Pikachu" mistake is just a little mistake (hey, I don't think many people noticed it the first time they watched the episode) and it isn't different from the other tiny mistakes that are in the other episodes (like coloring errors). Recycling the way the attacks look is like the oldest thing in this show. Most of the time, we only have Iwane's Aerial Ace, for example, or Iwane's Water Gun that makes Buizel get a blue eye =P. At least this time, they changed the scene a little, not only by removing Grandma and adding CotD there, but by making Piplup look down the hole, which was what he was doing at the time.
This episode was good. Not awesome, but good enough. This is one of those episodes that gives some time to shine to many characters of the group. We got Pachirisu, Buneary, Mamoswine, Monferno and Happiny doing something this time. Even Brock was useful. It's better to see them doing something once in a while. I really liked how Happiny just destroyed what was left of our mind after the opening by lifting an entire lake. With Team Rocket included.
The random battles of Magnezone and Metagross being just... random battles is also great. Usually, one of those is just angry/sad/whatever that its home/family is being invaded by the other or something like that, but this time they just wanted to fight. Wild Pokémon that just want to fight because they love to fight -I guess that isn't too common in the animé-world.
And the ending was awesome. Piplup and Gible are still great.
Loved the chance to hear that music from Movie 5 again.