An interesting read in general.
However, if much of the point of the article is to comment on how the Mythicals are (not) given plots or storylines, I find it a noticeable fault the lack of mention of the Mystery Dungeon games! Where a number of them were visibly involved storyline-wise, even if they are not playable. And "but spinoffs" is not an excuse because, well, Colosseum.
I'm not up to date on Mew but my understanding is it features heavily in the backstory of Super Mystery Dungeon, up to actually being one of the members of the classic hero-partner duo that makes the games' usual gameplay loop. Except, this time, Mew is stuck reincarnated as a Starter mon, so, even if a fine print, you do actually get to play with a Mythical in your team.
As for Celebi, the thingy features more heavily in the Explorers games, and is at some points part of the team (but as an assist; not directly playable). Celebi was the one who sent the player and Grovyle from the Dark Future to the past, as members of a sort of La Résistance. However Celebi can not itself travel in time, it seems, and thus you only get to play with him/her first when the plot takes you to the Dark Future, and second in one of the Special Episodes where you play Grovyle's side of the storyline.
Can't say much of Jirachi except that it shows up as a boss in Super, and is the goal of an expedition int the backstory of Explorers, where he grants one wish to the expedition's Bidoof (whom you'll later meet when you are a newbie at the Guild). Bidoof's wish was to have friends and it is mildly implied in the storyline that Jirachi fulfilled that wish by making you and your partner meet during Bidoof's Guild timeframe.
And that's the ones I remember.
...What's a "Volcanion", anyway?
