Mawile is a Generation III Pokémon, and it's clear Game Freak was already running out of interesting character design ideas back then. Mawile's pigtails look like a huge monster mouth, but according to her bio, they're actually horns. However, Mawile can still use them to bite opponents, which makes them a monster mouth in my book. Mawile is classified as a Deceiver Pokémon, which I'm guessing is just Game Freak's excuse for why nothing about this Pokémon makes any sense. It's all just an illusion! Or something.
Official Pokémon Rating: Monster Mouth!

Mega Mawile
When in doubt, add another monster mouth. It's obvious Game Freak didn't have any new ideas for Mega Mawile – her ability is called "Huge Power," for crying out loud. That's one step above naming an ability "Thing That Happens." On the plus side, Mega Mawhile's mouths do look scarier this time around. If nothing else, it beats having a tail stick out of the back of your head.
Official Pokémon Rating: Monster Mouth!...X2.

Lucario is widely thought to be based on the Egyptian god Anubis, but he reminds me more of Sly Cooper. Think I'm crazy? Consider this: Not only is Lucario an anthropomorphic creature that wears a mask and has a fondness for the color blue, but he stars in a manga called Phantom Thief Pokémon 7, in which he helps his trainer steal objects from other thieves and give them back to the people they were stolen from. An honorable thief, huh? Where have we heard that before...

Oh, the black things on Lucario's head also help him summon and use a special kind of aura energy, because...Pokémon.
Official Pokémon Rating: Knows How To Strike A Pose

Mega Lucario
Surprise, surprise: Another mega evolution that looks largely the same. Mega Lucario sports some extra spikes and a bushier tale, but the biggest change is his head thingies have grown bigger and float in the air. I'd be willing to completely write off Lucario's evolved form if it wasn't for his new special ability: Adaptability. Finally, something about Pokémon actually makes sense!
Official Pokémon Rating: Can't Mess With Evolution

If there's one Pokémon on this list that's in desperate need of evolving, it's Blaziken. Blaziken is a Blaze Pokémon, but unlike other cooler fire-based Pokémon like Charmander and Chimchar (a monkey whose butt is on fire), Blaziken has a weird '70s vibe going on. I'm not sure whether it's the bellbottoms, the long hair, or the wooly vest, but something isn't right. Oh, I know what it is – it's the furry crotch lump.
Official Pokémon Rating: You're Creeping Me Out, Dude

Mega Blaziken
Well, Mega Blaziken is a little better, I guess. He's still got the stupid vest and bellbottoms, but at least his hair is cooler, and he's got flames streaming off of his wrists. His new kung-fu pose is an improvement too. Still, Mega Blaziken's height, weight, and special ability are all the same as its regular form – I guess you're allowed to call anything Mega Evolution nowadays.
Official Pokémon Rating: Mega Disappointment

Despite my own encyclopedic knowledge of Pokémon, information for this article was taken from the official Pokémon X and Y website and Bulbapedia.