Headcanon- The Donatello Brothers
OOC- I was going to reference the Donatello Brothers, and then I thought I'd post about the origin of their name.
From http://rhythmthiefr.deviantart.com/art/The-Donatello-Brothers-Another-RhythmThief-FanFic-291187135?offset=50#comments
~rhythmthiefR Aug 6, 2012
I was the first to use the name, "Donatello Brothers", wrote this back in April, on the 20th if i remember correctly.
In fact, i created personalities for this, but i guess the fan base already had personalities down.
~rhythmthiefR Aug 7, 2012
Sure: here's my take on them.
I developed them as embodiements of the "left and right brain" concept, which states that people who are genetically created to think with their left brain are more logical, and right more creative.
Leonardo is the dominant brother, often commanding Gal around. He thinks the real world and facts are important and finds Galileo's novelty obsessions hard to understand. He is the embodiment of the "left brain". (the whole "leo and left both start with L" thing was not intentional, but a good way to remember it.)
Galileo is the inferior brother, but is more rebellious. He prefers fictional concepts and creativity, and despite the fact that he knows trivial things aren't important, he can't stand Leo's necessity for the real world. He is the embodiement of the "right brain".
The way i've seen people differentiate the two is by giving one of them really dark brown hair and the other midnight blue hair.
Personally I'm not keen on a strict division of character based on such a simple concept, and will go with whatever character comes to mind when I write, but the name and concept is good and people know to use it, and, importantly, there is a precedent of the name being used IC. So until people start playing these guys with different names, I will refer to them as Galileo and Leonardo Donatello, with a hat tip here to the originator of the name.
My headcanons (which anyone may adopt) are that they are also known as Phantom G and Phantom L, that they are experts in using the catacombs to get around unseen, that they are experts in silent communication with one another, and that they are quite a few years older than Raphael and taught him things.