On November 8, 2007 I wrote a post that talked about how social marketing "tests the concept of juristic personhood by daring brands to live up to their legal status." That's still true. But juristic personhood doesn't make one a person.
People have the ability to play against type. For instance, "The Natalie Portman Rap" isn't funny if it's not sung by the sweet, petite, Ivy Leaguer. And with apologies to Sarah Silverman, "I'm Fucking Matt Damon" would've been been a yawn if Hollywood nice-guy Matt Damon hadn't been singing backup.
I'm not sure this sort of self-referential riffing would work for brands. Consider Gatorade's spinoff G2. The G2 spots play on the core brand's athletic heritage, not against it. The copy includes the line, "You're always an athlete, hydrate like one." Can you imagine the same campaign with the tagline, "You're not always an athlete, so we made a drink for that, too."