While there are no lowercase characters in the Mixed Breed™ fonts, there are alternate versions of the uppercase characters in the lowercase character slots. Not only are the character shapes slightly different, but they are also have built-in baseline shifts, giving the set text a looser feel.
The general rule of thumb is to set your text in uppercase if you want a rigid baseline, and in lowercase if you want more of a bouncy effect. Try alternating between the two character sets if you have duplicate letters which appear side by side.
FULL CHARACTER SET
Each font in the Mixed Breed™ family has a full character set of 232+ letterforms, with all characters designed in the style of the font.