My green townie is called "Kermit".

My touring bike is called "Tipsy" because it falls over a lot.

My rain bike is called "Grimis" because it's purple and has fat tubes.

My chopper is called "Dewey" (spelled D-U-I) because that was the design inspiration and purpose.

I have 4 other bikes without names that are simply referred to by their make/model name or style.