Dr. Colloso is a broken Silver Marten. He has the eye circles and ear lacing of the tan pattern, but I'm not seeing any yellow/tan shading there. Without a good, dense black to compare to, it's hard to spot, but his body color just doesn't look like the black of an Otter (plus, if he was an Otter, he'd have a tan-colored triangle behind his ears, and you most likely would have mentioned that).
Most of the broken Dwarfs that I have seen are a bit short on color. With the broken pattern, the broken gene (En) sets the pattern, but there are a lot of modifiers that determine what the pattern looks like. The Dwarf Hotot was developed from the Netherland Dwarf, and I suspect a lot of the broken Dwarfs have some Hotot not so far back in their ancestry. The modifiers of the Dwarf Hotot reduce the color to just rings around the eyes; if a rabbit has just some of these modifiers, it makes sense that there wouldn't be a lot of color on other parts of the body. By definition, a Charlie is a rabbit that has two copies of the broken gene. By just about any breed's standards, your little guy has too much color to be a Charlie (which is good news for him, since Charlies almost always have the health problems that come from having two copies of the broken gene).
