Not really weird at all. Notched-Ear Pichu has a reason to differ from others since it's like a part of the movie special.
I do agree, it isn't weird at all for the Notch-Eared Pichu's sprite to be altered from the original Pichus. For one, like stated it is a movie event and the ear alone makes it differ from a shiny. Not to mention, I like the Notch-Eared Pichu's sprite better as well, and like I mentioned the ear was done very nicely. This is one Pokémon I won't mind having walk along side me in the game as it is pretty original from other Pichus.
1: I pity the poor fool who has to wear the Pichu costume.
2:If you look at the new map you can see the entrance into the temple where the event with Arceus takes place , it's at the bottom of Mt.Silver.
3:My theory about Cynthia being a time lord or deity seems to be gaining ground.
It is strange how you conclude the location to be at the bottom. As it is very clear [if this is Mt. Silver] that there may be more to it than before. For one, it is already shown Johto is expanded, and this doesn't exclude the caves and mountains either. The snow situated in the area and the way Mt. Silver was portrayed with ice caps gives good evidence of it, but I believe the area may be further into the mountain rather than exactly at the bottom.
As for Cynthia, she's a Champion, so she is prone to having the ability to travel. As the game says, trainers travel and experience an adventure. Not to forget that in the anime and the games Cynthia has interest in the three Deities and the folklore legend of it all. So, it makes sense Cynthia appears, but how she plays a role in all of it will be interesting.
Knowing as how Arceus brings birth to one of the three, the egg is more than likely it. So, this will be an interesting experience to actually hatch either a Dialga, Palkia, or Giratina. The event looks intriguing and the idea of having so many Unowns come about is simply applauding. GameFreak definitely found a great attraction for the game players and it seems as though they've extended the research on the Sinnoh legendaries with this basic connection.
As for the guy in the Pichu costume, I feel sorry for him as he must feel very hot in all of that.