A thread about discussing a sometimes occurring idea in the games that I'll call gameplay exceptions for sake of categorisation, and also visual exceptions I as found that there's many that are just visual. I'm defining these as specific stuff in the games that have some some kind of exception to how stuff of what they are expected function or defined as while still being that thing. To better explain the idea I'm trying to get across, here are some examples:

>Mega Rayquaza
Mega Rayquaza does not need a Mega Stone. Instead it Mega Evolves from knowing Dragon Ascent. It can also hold an Item while Mega Evolved because of that.
>Shedinja
Shedinja not only has 1 Base HP, but can never have more than 1 max HP as a result of bypassing the HP Stat calculation formula entirely, if it weren't for the latter the lowest HP it could have would be 11 HP. This has several strange and interesting results. Also, when Nincada Evolves to Ninjask, if the player has a Poké Ball and an empty spot in the Party, Shedinja just kind of, shows up.
>Diglett and Dugtrio
Diglett and Dugtrio have several gameplay exceptions and visual exceptions relating them always having to be on the ground. Some other similar Pokémon have some of them too. Those being Sandygast, Palossand, Wiglett, Wugtrio and Mega Gengar. Who are all also immune to Telekinesis and have a special animation of appearing out of the ground when exiting their ball.
>Calyrex
Calyrex uniquely gets a blue outline from Dynamax instead of what other Pokémon get.

These the kind of stuff I mean like how from these examples, Mega Rayquaza goes against the requirements of Mega Evolution but still is a Mega. It's unclear and debatable in some cases, for example I'm not sure if Spiky-eared Pichu counts or not for this.