If there's one thing that every Pokémon fan the world over knows (aside from how terrible a trainer Ash Ketchum was in the original animated series - seriously go back and get your Pidgeot, you idiot) it's the famous slogan of the entire series:
"Gotta Catch 'Em All"
This mantra, repeated over and over in the games, comics, shows, and movies is so deeply embedded, whenever a new video game rolls out it's impossible to resist hoarding all types of capture balls and stalking deep into the long grass for hours at a time.
However, there's a dark secret to all of this questing to become a tip-top trainer, and that's the simple fact that in reality, you're NOT going to be able to complete the entire Pokédex each and every game.
And it's not through lack of effort on your behalf! It's because GameFreak and Nintendo, being the sneaky little devils they are, decided long ago to reserve some Pokémon as "Event Exclusive", or to lock others behind long-since finished promotions.
Unless you went to each and every meet-up, bought every cross-branded item and attended every timed exclusive online session, your roster is going to look like Scyther has slashed a few holes in it.
10. Darkrai - Pokémon Diamond, Pearl & Platinum
When looking at Darkrai for the first time, you might immediately start looking at your team and questioning who to boot off to give this big bad lad a space to shine, as its edgelord design and rather horrifying description make quite the first impression.
Seriously according to the game this thing floats about at night stalking people and then invading their dreams to give them nightmares. It's like having a pocket-sized Freddy Kreuger!
However, I'll have to wake you from this dream with the knowledge that in order to claim one in either Diamond, Pearl, or Platinum, you'd need to have a Members Card in your possession, which unfortunately was an event-exclusive item that only circulated briefly in late 2009, for just a few months.
According to various sources, Darkrai is completely unobtainable by other legitimate means, leaving the otherwise cool creature to be unfairly slept on.