There is a fairly cool creature from Nyabme (african-styled) campaign setting for D&D 3.5 - a glowing frog.3.5 statistics and description
(it's a translation, but there is full original text in small font)
Also, I made a 4E conversion of it. I generally don't like this new edition, but I have to say - building a monster was easy. (Well, it's an easy monster with no tricky powers. I feel a little clueless thinking of how I would represent more unusual powers in this strict system...)
It came out like that:
Glowing Frog Level 1 Controller
Tiny fey magical beast XP 100
Initiative +4 Senses Perception +3, darkvision;
HP 20; Bloodied 10
AC 15; Fortitude 10, Reflex 17, Will 16
Speed 2, swim 4
Hypnotic Colors (standard;at-will) Psychic
Burst 3; targets enemies; +5 vs. Will; target is dazed (save ends).
Glow (standard; at-will)
Burst 6; +5 vs. Fort; target takes 2 ongoing fire damage (save ends).
Invisibility (standard; at-will) Illusion
The glowing frog turns invisible until it attacks.
Alignment Good Languages Draconic, Sylvan
Str 3 (–4) Dex 18 (+4) Wis 16 (+3)
Con 4 (-3) Int 12 (+1) Cha 14 (+2)
/Details on telepathy, constant glow and tactics./
See, I had to change or omit some of abilities (Animal Trance, Detect Evil...) to get this creature function properly in the context of D&D 4E. More ActionRPG-ish, less western-style RPG-ish.
Then I decided to make a conversion to Eldritch, too. I could make Glow ability sap Resilience (or Health DP, for I use homerule that differentiates magical and bodily resistance). I could redefine Animal Trance ability as affecting "small or otherwise harmless animals", leaving harmlessness measurement to the GM.
But then I thought that system-specific changes should help system's style. D&D 3.5 is action- and interaction-oriented (as I see it), D&D4 is combat-oriented.
(All conclusions following this line are based strictly on my experience, thus IMHO.)
Eldritch, on the other hand, is adventure-oriented. It's meant to accurately represent character abilities and to deal with combat fast and cinematic. So, it won't be fun when glowing frogs will pile up on party and hypnotize/glow them to death, which can take many boring combat rounds.
Should the Eldrtich-converted glowing frog do more damage with Glow to make potential combat more swift or on the contrary - should this ability be considered harmless unless frogs hypnotize you to stay still? Maybe more stress should be put on invisibility and diplomatic abilities, so the frogs won't be combatants but rather sneaks? How to represent Animal Trance?
This is really a mind training, not a practical question... Not that I need this frog for my current game or something... Just stretching my brain muscles %)