Mercedes Griffin (Carlie Casey) is Arthur Griffin's daughter. In "Big Time Demos," she pretended to be the "secret someone who picks the demos." She also dates all members of the band, except James, because she never dates "anyone prettier than her." She re-appears in "Big Time Party" where she is on a date with Logan, but when she finds out he is trying to date her and Camille at the same time, she breaks up with him and starts dating "Guitar Dude", but it is never officially acknowledged. She is at least 16. She likes manipulating people also. Mercedes is very vain as shown in "Big Time Demos" when she said that "I don't want to touch other people's butt sweat."