Today I will tell you all results about my researches about sprites in areas. This is a bit better than the last time because I can do many more things. So here we go
I will explain my stuffs with the code's image in the last post. A sprite's pattern has always 16 series of 4 bytes. I will pick up a serie and explain each byte because there is a utility for each one. The 1st  is the id of the "spritesheet", it's connected with the 2nd  which is a variant index of the "spritesheet". The two bytes decide which sprite will be shown. In this case,  is a normal Toad in Toad Town and  next to it decides he is red. With the second you can, generaly, change the color of the sprites like : Ninjakoopas, Shy Guys, Clubbas, etc... The 3rd  determines which animation will be played,  is generaly an idle animation. The 4th  separates two series. In function of which animation the sprite will play, it will load the approppriate serie.
When you enter into a area (or get out from a battle) the sprite will load its spritesheet once and from a specific serie. If you enter into an area (or run away) the sprite will load the #1 serie to play the idle animation. Afterward if the sprite chases you, it loads the #4 but don't refresh its spritesheet, but it DOES for the variant byte. You should just replace all of firsts 2 bytes if you want to deal easily with it.
So, do we need all theses 16 series? The answer is I'm not sure, but I'm pretty sure there are similitaries for some of them. I do a list with all functions of them from 1 to 16 :
#1 : Idle & Run Away
#2 : Walk
#4 : Chase
#7 : Death*
#8 : Hit
#9 : Before Attack
#11: After Attack
Death is only used to load the variant and the animation.
There can be more functions, I would need to do more tests. Notice, they are for ennemies, that involves exceptions.
For NPC, there are functions to load animations which aren't in the patterns. Example : if you want to talk to a NPC, a function above the pattern will load an animation. In some cases, one function can load animations for many sprites.
Now, I will talk about the big issue you can have with messing with sprites. According to me, the game has a limit about the number of spritesheets it can load. More you load spritesheets, more it leads to a crash. Worse than that, some of spritesheets (especialy the bosses) are heavier than normal ennemies. That's means if you can load maybe 5 SS you can barely load 2 bosses (which explains why I was just able to load General Guy). However, the number of sprites which have a heavy SS doesn't matters and to have many variants with the same SS doesn't count as loadings.
I would add all that stuffs can be use to search data linked to animations in area's data and ennemy's data. That's all for now, there is a image of what it looks like if you're lucky, because of that limitation. See you next time