| Episode cast overview, first billed only: | |||
| Blake Lively | ... | Serena van der Woodsen | |
| Leighton Meester | ... | Blair Waldorf | |
| Penn Badgley | ... | Dan Humphrey | |
| Chace Crawford | ... | Nate Archibald | |
| Taylor Momsen | ... | Jenny Humphrey | |
| Ed Westwick | ... | Chuck Bass | |
| Jessica Szohr | ... | Vanessa Abrams | |
| Kelly Rutherford | ... | Lily van der Woodsen (credit only) | |
| Matthew Settle | ... | Rufus Humphrey | |
| Desmond Harrington | ... | Jack Bass | |
| Connor Paolo | ... | Eric van der Woodsen | |
| Zuzanna Szadkowski | ... | Dorota Kishlovsky | |
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Megan Guinan | ... | Willa Weinstein |
| Sonya Harum | ... | Sophie | |
| Luke Kleintank | ... | Elliot Leichter | |
Chuck and Blair are faced with the most difficult decision they have ever faced as a couple. Serena plans a surprise birthday party for Nate, but Jenny does her best to sabotage Serenas's efforts. Dan and Vanessa's new relationship hits a bump in the road. Written by CW Publicity