| Name | Character |
| Zac Efron | Mike O’Donnell @ 17 (1989) |
| Zac Efron | Mike O’Donnell/Mark Freemann @ 17 (2008) |
| Matthew Perry | Mike O’Donnell @ 36 (2008) |
| Leslie Mann | Scarlett O’Donnell @ 36 (2008) |
| Scarlett O’Donnell @ 17 (1989) | |
| Michelle Trachtenberg | Maggie O’Donnell |
| Sterling Knight | Alex O’Donnell |
| Thomas Lennon | Ned Freedman @ 36 (2008) |
| Tyler Steelman | Ned Freedman @ 17 (1989) |
| Hunter Parrish | Stan |
| Melora Hardin | Julie Goodwin |
| Margaret Cho | Mrs. Dell |
| Jim Gaffigan | Coach Harvey |
Status: 26 Jan 2008
Information about Thomas Lennon, Hunter Parrish, Margaret Cho & Jim Gaffigan courtesy of Meg @ Livejournal. Additionally, Zac has mentioned the Hunter Parrish casting in an extra interview during the HSM2 DVD launch and the casting of Thomas Lennon was mentioned in an article in Entertainment Weekly.
26 January 2008
17 Again