thank you!! i basically just used the edit image from dialog hack and the permanent items hacks, so the cats are basically blank items that change their image when u talk to a lantern (and then its just some variables to make sure that the cats appear in the order i've chosen) so yeah you grab the matches, the variable on the matches gives you the diff lantern dialogue with the hack info that changes the lantern's image + colour and also makes a cat appear :P
you can use sprites of course but for this illusion i needed items so that you can walk on them so it truly appears like the cats just appear where there was nothing. there's probably some way to make them actually be like a 'wall' through js or something but i dont know how to do that and just experiment with the hacks that already exist (i'm sure sean might make a hack that toggles the 'wall' property of a item one of these days)- just be sure that if you want to make like 5 items appear one by one, each of those items are a different one else the hack modified the specific item so if u have more than one instance of it in your game, it'll change it everywhere (sprites can be put more than once so thats not an issue)
i hope this is a decent explanation! i spend a lot of time figuring this out for my other game robits and had a lot of trial and error for some things that seem rly simple >.<;;
oh! also borksy is great if you dont kno abt it- makes it real easy to add hacks to test your game. you can add the edit image from dialogue hack into the 'Additional JavaScript' section and the permanent items hack is already in the hacks section just be sure to read the options for it where you can choose to have it be for all items or the default is that you have to put PERMANENT into an item's name
sorry if you already knew abt borksy >.<;; i just use it a lot because its a huge time saver... ah i remember the days i had to manually insert all the hacks into the downloaded html file just to test it.... that was so long ago.... back in... march of this year xD