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Step 12: There's stunt casting, and then there's good stunt casting
Bringing Hilary Duff aboard for a few episodes this season has been a great example. She seems to be a good match for Dan, and she actually gets extended interaction with the other characters and doesn't just stick out like a sore thumb. We love us some Posh Spice. Give her an extended cameo so she doesn't just join the ranks of the fly-by-nights this season: Tyra Banks, Tory Burch, Georgina Chapman, Cyndi Lauper, Sonic Youth and Lady Gaga. Though if the next Spice Girl reunion came together on the Upper East Side ... .