Meh.  I prefer Bidoof.

No.

What, you want more?

Fine.  What do we know about Mewtwo? He was created in a lab by manipulating Mew’s DNA to create the ‘most powerful Pokémon in the world.’  Now, to me it seems likely that what they were primarily aiming for was pure offensive might, so perhaps they were willing to sacrifice a little of Mew’s resilience (and it’s not a huge sacrifice; Mewtwo’s physical defence is still pretty good) for larger gains in psychic power.  More to the point, Mewtwo’s origin story is essentially a somewhat ham-fisted fable about the dangers of ‘playing god’ with genetics; to me it makes perfect sense that the resulting creation might have some flaws that would not have been apparent in advance.

Eh… well, the thing about Meganium is that her main problem is a bad movepool, and Mega Evolution doesn’t actually do anything to fix that.  Adding a new type to her would be nice, but it’s also kind of difficult because she doesn’t really learn any attacks outside of Grass and Ground (due to the rule that Grass-types Don’t Get Nice Things), and I don’t know if Ground makes sense for her.  Mostly Meganium trades on her support attacks – Aromatherapy, Leech Seed, Dragon Tail, that sort of thing – so buffing her defences is kind of a no-brainer, and a nice defensive ability like Filter can’t hurt.  Something like Grass Pelt might be more flavour-appropriate, but it’s not like Filter really has a consistent link to any particular kind of power anyway (I mean, Mr. Mime and Mega Aggron?  What’s the common theme there?).

Well, in fairness, is “stiffen[ing] all the muscles in its body to raise its Defense stat” really any more ridiculous than all of the other stuff Butterfree can do?  Whirlwind, Solarbeam, Dream Eater?  Electroweb, for goodness’ sake?  I mean, the fact that Butterfree can learn Electroweb surely implies that she can still produce silk of some kind, even though we don’t normally expect adult lepidopterans to do that.  Gorebyss seems weird, but she actually has a higher physical defence score than Clamperl, so there isn’t really any reason Iron Defence should be inappropriate (especially since, on really any non-Steel-type, we should probably assume that it’s magic).  And Gorebyss does in fact have shells; they’re just this… kinda weird… impractical bra thing.  Actually harder to explain Huntail, but again, very high physical defence stat there.  Maybe they both have calcareous scales or something.  As for Shroomish and Focus Punch… well, this is why I normally refuse to deal with specific moves on specific Pokémon.

Funnily enough, I’m kind of okay with the idea of Mega Blissey being a thing, because at the moment we have this weird situation where Blissey is actually overshadowed by Eviolite Chansey, because Blissey’s main advantages over Chansey are greater special attack (who cares?) and Leftovers (meh, they have Softboiled).  That… brings up an interesting point.  Evolving into Blissey doesn’t actually make Chansey significantly better at her core role: her HP and defence only increase by minuscule amounts, and Chansey is already so good at special defence that Blissey’s extra points aren’t a huge deal (besides, Eviolite).  The real difference is that Blissey can actually use attacks.  So… if we’re doing a Mega Blissey, why not embrace that?  Put most of her mega evolution bonus points into special attack and speed.  Either leave her other stats as-is or only give token increases, maybe even cut her special defence a bit (there’s precedent for that; Mega Garchomp is slower than regular Garchomp).  Looking at something like [255/15/15/135/120/100].  Do some kind of vaguely seraphic design, lots of feathers and too many wings.  Add some gold to the colour scheme.  Make Serene Grace her sole ability, or even make a jacked-up version that triples the odds of weird stuff happening, just for fun (Thunder with 90% paralysis chance FTW!) – if that sounds like too much, remember that Blissey has no good special STAB; even if we go Normal/Fairy she’s only got Dazzling Gleam, which doesn’t synergise with Serene Grace (EDIT: correction; Alpha Sapphire and Omega Ruby have a move tutor for Hyper Voice – still, that doesn’t work with Serene Grace either).  If there is even a slight chance of a weird-ass [Gravity – Blizzard – Thunder – Fire Blast] set becoming a thing, I’ll be happy.

Hmm.  Interesting that you would single out Electrode.  Why?  Isn’t it a little bizarre that any Pokémon can use Rain Dance at all?  Even for a Water-type, altering weather patterns is a fairly spectacular application of power that ought to have wide-reaching ecological impacts – let alone for the frankly ridiculous array of other Pokémon that somehow have access to this thing (pretty much “everything that isn’t a Grass- or Fire-type, and some things that are”).

I’m inclined to think that you’re asking about Electrode specifically because it’s so odd to imagine Electrode ‘dancing,’ but I really don’t think this is the right question.  In Japanese, Rain Dance is called Amagoi, which Bulbapedia translates as “Rain Prayer” – as far as I can tell (bearing in mind that I cannot speak or read Japanese), it seems to be a generic term for any sort of rainmaking ceremony; “Rain Dance” is really the best equivalent we have in English because it gets across the sense of ritual, of the invocation of some kind of god or spirit – in that sense I actually think it’s quite an apt translation, although it’s unfortunate that it comes packaged with those connotations of lively physical activity.  Most of the other European languages into which Pokémon is translated seem to do the same thing as English – Regentanz, Danse Pluie, Χορός Βροχής, Danza lluvia and Dança da Chuva all include the word for “dance” and all have a meaning that goes back well before Pokémon, probably as a direct result of influence from the English phrase (with the odd exception of Pioggiadanza, which has the same literal meaning but, as far as I can tell, is a brand of shampoo).  It probably isn’t necessary, in fact, to imagine the Pokémon dancing as they use this move – we can, and some of them very well may if they find it appropriate, but it’s likely that others chant, or pray in silence, or some combination, or something completely different.  The common thread with all of them, what they’re all doing the same, is the sense of appeal to a higher power of some description.  The details of how the invocation works may not be terribly relevant.

In short, the answer to your question is “the same way as everyone else!”

Eh… hmm… that’s a tricky one.  Victreebel’s a pitcher plant, yeah?  Well… maybe it would be neat if… hmm… there’s a kind of pitcher plant called a ‘cobra lily,’ because its leaves look sort of like the hood of a rearing cobra.  What if that long vine that on Victreebel’s head that it uses for attacks like Vine Whip and Slam actually took on a life of its own and grew a little serpent head on the end?  It’s used to lure prey into Victreebel’s ravenous maw, and can attack on its own as well.  Eh… I don’t know if I like the idea of giving a mega evolution features that are most interesting in terms of how they’d work in the wild, though, since wild Pokémon don’t do that.  Mrrm.  Dunno.

Mostly along the lines of “MUWHAHAHAHAHAHAHA!”

I’ve thought about it.  Not sure how I feel, all things considered.  If there are obvious visual differences, then I don’t think there’s really any inherent balance issue from a competitive standpoint (assuming we even care about that at all).  It’d allow the introduction of regional variations, which would be nice.  I guess the main question is whether doing this would take away from time spent designing completely new Pokémon, and I don’t really think that it would.  Personally I’ve always thought it would be really funny to have a Psychic Nidoran variant, for no other reason than because male Nidoran can inexplicably get Confusion as an egg move.  Maybe that’s one way you could access these variant forms?  By breeding in an egg move that would normally be hilariously suboptimal for that species?  Then again, if you have a lot of these, then it will start to get silly… we’ve already got stats and movepools for seven hundred of the damn things to keep track of…

If there is some special link between the two, nothing else hints at it… The golems were sealed away deliberately, so I would presume that the people responsible for that are also the ones who determined the mechanics of the lock; they probably chose Relicanth and Wailord for some reason.  They might have picked Wailord as being the largest Pokémon they knew of (and therefore strongest) and Relicanth as the oldest (and therefore wisest).  Alternatively, since the inscriptions claim that people actually lived in the chamber where the lock is located – which is at the bottom of the ocean – Wailord and Relicanth may both have been Pokémon that were central to their culture and way of life.  Or maybe it was that a Relicanth and a Wailord played an important part in subduing the golems and allowing them to be sealed away in the first place, and the people who built the lock wanted to honour them by making them the Pokémon that would open it.  Take your pick; not sure there’s enough information to be more definite.