Ms. Brown was an M&M introduced in early 2012 in a Super Bowl XLVI commercial. That's how we found out the face of the brown M&M.
Ms. Brown first appeared in a Super Bowl XLVI commercial where everybody at a party thought she was naked, including Red, who took off his shell and danced to LMFAO's I'm Sexy and I Know It. You ever think how weird that marketing was? It's kind of fucked.
Ms. Brown appeared in more commercials to promote finding an "all brown" bag of M&Ms, as well as 'The Apprentice'.
Hey kids! You like bags? Edit
Ms. Brown only appears on the bag for mint flavored M&Ms, which are rare. She appears alongside Ms. Green on the wrappers.