Just a list of rare/friendly monsters.
Mecha Knight Kit
Tortodrone
Vog Cub
Love Puppy
Mewkat
Gold Trojan
Impostocube
Rock Jelly Cube
Sloom
Sloombargo
Soul Jelly
Oiler Baron
Quite a few of them, aren't there? Except for the Mecha Knight Kit, I've hardly seen any of them. I've only seen a Mewkat, Impostocubes, and a Rock Jelly myself.
sigh, here we go again... the only rare monsters are ones that can randomly spawn in the place of another or can be found in a monster cage. the list is as follows: soul jelly, sloom, rock jelly, impostocube, mewkat, and love puppy.
I saw my first soul jelly in FSC the other day (ironic, since I never saw any while rabidly doing JK, but now that I'm doing dungeons where there's maybe 10 jellies in the entire place...), and I loved the little skull it drops.
I don't think I've ever seen a mewkat and I've definitely never seen a sloom. Do they even exist anymore? Sleep was taken out of the game, so many slooms went with that.
English debate:
Mecha Knight Kit means a.... kit to build a mecha knight(duh). The robot itself should have a different name.
Tortodrones are more extinct than rare right now, really.
I'm hoping to see a Mewkat sometime - the other non-hostile rare monster! :3
I've seen four- ...well, I've encountered four Love Puppies so far, I've seen three of them because some jerk mercilessly crushed the fourth one while offscreen.
I wonder if a "Rare Monster" Wiki page would be of any use to anyone. Clear some things up with a list for the actual "Rare" Monsters and "Currently Non-existant" Monsters.
Mecha Knight Kits drop all the time, not rare, and most people ignore them (I personally hate Uncle Robo Bad Touch--shocks, blocks shots, etc.).
Tortodrones, Vog Vubs, Gold Trojans, Sloombargos and Oiler Barons are not currently in the game and are therefore not rare, because they cannot be found at all.
Slooms can sometimes appear from monster boxes, so those are pretty rare.
Love Puppies, Mewkats, Impostocubes, Rock Jellies (spawn from blocks), and Soul Jellies sometimes spawn in place of their regular counterparts, so you could call them rare (except for Rock Jellies, which are all over the place in Grim Gallery).
Otherwise, not sure what you're going for. :)