Strange things, aren't they?

OH MY GOD ANON YOU DON'T KNOW ABOUT DECAMARKS.... allow me to inform you.

decamark(s), also known as ten question marks (??????????) is a gen 3 glitch pokemon. decamarks is a fan nickname since saying ?????????? is kinda hard. similar to missingno, decamarks is a placeholder pokemon programmed for crash handling purposes—if the game tries to load invalid pokemon data, decamarks will pop up!

there are a LOT of different kinds of decamarks. gen 3 games used hex values 0000 to FFFF to represent different species of pokemon, and only 439 of those slots are actually assigned to a pokemon. that means there are 65,097 different kinds of decamarks!! they all have different kinds of effects depending on which hex value you have.

decamarks can be exploited for a LOT of different stuff, some more useful than others. they're used in pomeg data corruption/glitzer popping, arbitrary code execution, all sorts of stuff. a lot of decamarks variants will just crash or corrupt the game randomly, but some can do crazy stuff! (here's a whole video of a few different decamarks) there are WAY too many different effects to even begin to talk about, so here's just one that i think it's hilarious.

the decamarks of transing your gender and subsequently ruining your game. this pokemon is great (source)

decamarks hex 0000 is a special decamarks variant, because it's the only glitch pokemon with an actual programmed pokedex entry!! this is the coolest and freakiest thing ever. it's so mysterious and deliberately vague that it's genuinely kinda creepy.

it's not nearly as interesting in firered/leafgreen though, since it kinda just... freaks out at you. it's programmed with the same dex entry, but it doesn't show up in that game LOL.

fun fact: decamarks isn't exclusive to the gen 3 main games! it actually makes a (vague) appearance in mystery dungeon rescue team as a glitch pokemon. it even has dialogue, which i think is completely hilarious. i think "Something..." is a very inspiring quote that we can all live by.

great question!! the best resource right off the bat would be if you the glitch city wiki; a live archive of the old glitch city labs wiki. it has all the glitch information you could ever want and more...

bulbapedia's glitchdex project is also really good. it doesn't have as much technical information as glitch city does, instead covering glitches more generally; if you don't have much knowledge about glitch pokemon already, i highly recommend skimming through the articles on there because it's a LOT of fun.

if you want to watch videos about pokemon glitches, check out crystal_, thezzazzglitch, and chickasaurusGL! all really excellent channels with a bounty of strange glitch content to explore. =) i hope you have fun learning more about these funny quirks and curiosities of the pokemon world...

!! THANK YOU SO MUCH!!! ^u^ your taste is impeccable; decamarks is truly one of the best pokemon that isn't even a pokemon <3