Rob Lowe, The West Wing
It's official: As speculated ever since it was announced that this is The West Wing's final season, original cast member Rob Lowe will return for the series' last two episodes, reprising his role of Sam Seaborn. Also resurfacing for one or more of West Wing's final five episodes are Mary-Louise Parker, Anna Deavere Smith, Emily Procter, Marlee Matlin, Gary Cole, Tim Matheson, Timothy Busfield and Annabeth Gish. But, alas, no Mrs. Landingham; besides being, well, dead, she's also busy yelling at the Scavo kids.