If it's fire red then we'll need 386. Not that it's necessary but you shouldn't just hack part of the game :P
Uhh okay 110... other ones...
Squiddles for like all the fish pokemon (or like Unknown or something). 15 Felt. Lil Cal and the millions of different types of him all floating around the inciphisphere. It could make like, idk, 4 versions? Same with Liv Tyler. There are I believe 5 versions so far, and if the bunny that Jane has is also of the same chain, 6.
Since GT is the final evolution, all of the guardians and ancestors are free, making for 28 extra characters (32 if A1 is ever shown)
There are also 12 lusii! Their sprite forms = 11 more since Aradia's isn't one.
Horrorterrors could make for as many as you want as well. They could also be a final evolution of any squiddles, if you don't want to make any direct references to Sandswept (which I do not recommend :P)
UU/uu. I'll count it as 2 regardless of how many bodies they have.
Other Aradia forms: Dead Aradia, Sprite Aradia, Robo Aradia. Also you could count the frog sprite by itself.
4 Midnight Crew members with 2 forms each because B1 and B2 are mostly the same.
5 exiles B2, plus Serenity.
4 known consorts and 12 known denizens.
4 types of chess pieces, both Prospit and Derse. Then the Black/White Kings and Queens of the three sessions (only White Queen B2). WK is the same form as an exile (since he's only an exile for 12 seconds), but there are prototyped forms for all 4 of them in A2 and B1. This makes 16 more.
10 types of
Underlings, 5 of them unnamed however.
Then there's the wacky stuff. The Cthulhu doll, the Harlequin Doll and then --> Harlequin Sprite pre-entry -- Harlequin Sprite post-entry (you know with the tail and full body). The crow --> seppucrow --> Crow sprite. Then Lil Cal sprite from that alt. timeline. Also Maplehoof, Dave's brain, Robo Troll (the generic one Equius made), Robo Jade, Robo Dirk, Autoresponder, Sawtooth, Buzzsaw, the Imperial Drone and the special Crocker Drone, the whale lusus that Eridan killed, fedorafreak, and Dennis from Gamebro.
If you want the missing 100, there are other ways:
If you do lots of squiddles you also get Princess Berryboo, the Murky Brineswallow, Skipper Plumbthroat, and Billy the Bellsuit Diver. 4
Sweet Bro, Hella Jeff (both of which have furry forms), Geromy, The Big Man, Peaches the Dog, the Slunk. 8
Characters in Jailbreak: The Guy (there's 2 guys but they look the same so it's like one species of Pokemon :P), The guy with pumpkin armor, Logorg, Drillgorg, the pony (no elf because I am trying to count let me count how I want :P) 5
Characters in Bard's Quest: I haven't read this in a loooooooong time, but iirc, there was the Bard, the King, the King's "body"-guards, and the shopkeep guy. 4
Problem Sleuth characters: this... is going to be difficult to accurately count. I will only count 3 forms for the main characters PS, AD, PI, but I will count Fiesta Ace Dick and Godhead PI as separate characters. Then there's female versions of 3 of them, Honeybee Professor, the 4 heroes (this is where the elf goes), the Weasel King, Death, the Candy Mecha, the Devil, the Demimonde Goddess, Wifehearst, and Bathearst. There are more but that is already 29.
There are 28 members of the Music Team and 14 members of the Art Team
Yeah anyway it would not be too hard to get to 386. I am missing several background characters from each adventure and the evolutions of the music team members :P