* Kiki Dee: played Tia, one of the twins
* Ike Eisenmann: played Tony, the other twin
* Ray Milland: played Aristotle Bolt, a scientist searching for the twins
* Donald Pleasence: played the villainous Lucas Deranian
* Eddie Albert: played the kindly, but eccentric, Dr. Stuart
* Kim Richards: played the mysterious, and somewhat villainous, "Witch Mountain" girl
* Dennis Hopper: played the "Witch Mountain" boy
Let me know if you'd like to know more about any of the characters or actors!