Ummm, your totally wrong. Jigglypuff was the second most popular pokemon in Japan who rivaled Pikachu's popularity. The reason Pokemon are featured in the animes and movies is because they are popular or are legendary. The reason Lucario was added is because he was popular; the movie is evidence to this.
Ummm...wow. I'm done. By your logic, only popular Pokémon are included in the anime...so everyone of them must be the bees v@gin@ then. Cause all of them are and will be featured.
Lesser Pokémon like Ditto and Shuckle have even had episodes solely based on them...not because, ya know, every Pokémon is to be featured at some point, but because that particular Pokémon is more popular than the others.
Lucario being featured only because its popular? Do you even watch or play Pokémon?! The animé was always going to feature Lucario at some point because at least TWO characters from the game use Lucario as their main Pokémon, and both of those characters had to be featured in the animé, so of course, Lucario would be.
Why was Magmar first featured on the show? Popularity? No, because it was a feature Pokémon for a Gym Battle.
Why was Dratini featured in the anime? Because it was hyper popular? No, because it was a feature Pokémon for the Safari Zone episode, where in the video games, Dratini can be found.
Why was Farfetch'd featured in an episode of Pokémon? Because it was popular? Do you even know WTF a Farfetch'd is?! It's the example of anti-popularity...and it had an entire episode based on it.
Popularity make the Pokémon appear in the animé? So why has Ratatta, Weedle, Qwilfish, LUVDISC...God, so many unpopular Pokémon have appeared with entire episodes dedicated only to them!!
Face it, Pokémon are introduced in the cartoon because its a show about POKEMON! Even the most useless, most forgettable Pokémon have been, or will be (in the case of Diamond/Pearl) featured in this show!
The show's about three trainers travelling around catching and battling monsters. Each season is like 60 episodes, with 3-5 seasons per generation. You know the writers are going to have room for every single Pokémon to appear, and not just the ones that are Legendary or "popular". Jigglypuff was no different. The animé just cemented its "then" popularity.
Close to 500 Pokémon, and at least 440 of them have appeared within the show or the movies...and still counting...and
only the popular ones are to appear on the show...