| Alan Alda | Mystery Guest Star | |
| Jason Biggs | Mystery Guest Star | |
| Zoe Caldwell During previews | Mystery Guest Star | |
| Glenn Close | Mystery Guest Star | |
| Jeff Goldblum | Mystery Guest Star | |
| Holly Hunter | Mystery Guest Star | |
| Nathan Lane During previews | Mystery Guest Star | |
| John Lithgow | Mystery Guest Star | |
| Eric McCormack | Mystery Guest Star | |
| John McEnroe | Mystery Guest Star | |
| Roger Moore | Mystery Guest Star | |
| During previews | Mystery Guest Star | (Mar 7, 2003 - ?) |
| Liam Neeson During previews | Mystery Guest Star | |
| Rosie Perez | Mystery Guest Star | |
| Al Roker | Mystery Guest Star | |
| Paul Rudd | Mystery Guest Star |