The illusion where Stephen Mulhern saws Mischa Barton into three and removes her middle section is called the "Sawing in Thirds" or "Center Cut" illusion.
The trick where Mischa Barton threaded a length of dental floss through the hole in her pierced ear, tied it in a knot and then pulled it out without ripping her earlobe was originally performed by Jane Curtin on a 1990 Penn & Teller TV special. In order to perform the trick, Mischa had to have her ears pierced especially a few weeks beforehand. Having kept them pierced for the photoshoot for her 2005/6 Accessorize advertising campaign, she then let them heal up again, and didn't get them re-pierced until 2009.
Mischa Barton: So, Amy, I see you've also practised self-mutilation for the sake of fashion - You have pierced ears like I do.