The basis of the Pokewalker isn't entirely new and is not like a Tamigotchi or similar toy. The Pokewalker is based on Pokemon Pikachu, which was a small Game Boy like device containing a Pikachu that you could interact with in small simple games. You could unlock more games by accuring watts, which were earned by walking as it had a pedometer in it. Also with the Pokemon Pikachu 2 GS you could interact with Gold/Silver/Crystal by the mystery gift option using the IR port built into the Game Boy Color. The reason I say this is different from a Tamigotchi or similar digital pet toy is because you never had to feed, clean up, or anything like that and it's purpose was supposed to be a fitness toy, which is why it had a pedometer.
The games in the Pokewalker are much simpler though being just an item finding game and a catching game.
Also in the games Team Rocket has been gone ever since Gold/Silver/Crystal. Ruby/Sapphire/Emerald had Team Magma and Team Aqua where Diamond/Pearl/Platinum had Team Galaxy. From what I understand of the anime Team Rocket has also become less important with just Jesse, James, Meowth, Wobbuffet and friends bumbling about on their quest to catch Pikachu and the real bad guys have been the new evil team from the game. I was never really into the anime and just saw random episodes from throughout the 12 seasons (I should note seasons here just means they moved to a new English opening [I'm totally serious] with most being about 50 episodes and the largest being Indigo League [the first] at 80 episodes [82 in Japan]) every now and then. Personally I've enjoyed the films (13th film coming out in July in Japan following the one film a year Pokemon has had) though, they usually have some cool animation in them that you don't see in the anime much.
As for the games at least Pokemon still has been pretty much as popular as ever. Last month Heart Gold and Soul Silver together were the #1 selling game in the U.S. during March according to NPD Group numbers (Note NPD doesn't count all retailers) selling over 1.8 million (about 1 million being Soul Silver) selling over 500 000 more than the next best selling game being FFXIII with over 1.3 million (about 830 000 being on PS3) with number three being GOW3 at 1.1 million.
The sales of Heart Gold and Soul Silver in their opening month is almost identical to Diamond and Pearl when they first came out and they will continue to sell quite well for most of the rest of the year probably. (Maybe not enough to get on the top 10 of the NPD list but still a hefty amont of units.) *Also neat bit of trivia Diamond and Pearl have been the most successful Pokemon release having sold 15 million units to date.
Also this is somewhat of an anal correction but the currently airing season of Pokemon is called Galactic Battles not Diamond and Pearl. (that was the title two seasons prior to that)
Oh and the change to fully polygonal backgrounds is the next logical step from the pseudo-3D perspective (the effect is established by a change in viewpoint and is still sprite based) that was introduced in this currerent (4th) generation of Pokemon.
Oh and about internet memes (the nice boat reference, which originated on /b/) a diligent player will find that in Diamond and Pearl the lead localizer Nob Ogasawara added in some references to memes from Something Awful. (He's a member of the forum)
" @Konanda: Nice speech but would it not have been appropriate in one of these threads? because this is more about the anime rather then the games even though they do reflect on the storyline of the series :) "