The porygon I got from the game corner has been trying to possess my Pokedex. I’ve heard of rotom occasionally trying to do this, but what would happen if porygon managed to? Is there risk to porygon or the data in the ‘dex?

It certainly depends on whether or not you plan on evolving it. A porygon by itself is actually a rather obedient pokémon and will follow your instructions to the letter. It’s simply attempting to integrate with what it perceives to be a more comfortable environment, and once it’s there, any risk to the health of either the porygon or your pokédex is rather minimal, as your porygon will work alongside your pokédex’s software and thrive in its native format. In short, you very likely won’t even notice it, save for possibly a slight increase in your pokédex’s efficiency.

Should you upgrade your pokédex with a porygon inside it, however, this will still satisfy its requirements for evolution, even though you haven’t given it its upgrade software or sent it through a trading machine. Some trainers even find this a more approachable alternative to purchasing a separate upgrade and finding a trainer with whom to trade. Additionally, once evolved, porygon2 gains a more refined AI, which is designed specifically to go out of its way to help its trainer in any way possible. Thus, a pokédex containing a porygon2 will perform better and faster than a pokédex with a porygon or an uninhabited pokédex, all because the porygon2 within it is better at understanding and executing commands than its predecessor or the pokédex alone.

However, once upgraded, be sure to withdraw your porygon2 from your pokédex before attempting any further upgrades, and beware of any downloads you receive on your device. Any upgrades will result in your porygon2 evolving into porygon-z, which…

Let’s just say that porygon-z goes to considerable lengths to do anything but behave in a way that makes remote sense. In the best case scenario, it may manifest a Zap Cannon from within the confines of your device’s hardware, resulting in the destruction of your device (and possibly your bag and its contents). In what’s not quite the worst case scenario but the scenario that’s significantly less appealing, your pokédex will automatically take you to the strange parts of YouTube every time you try to look up an entry. Maybe. There are … there are cases worse than that, actually.