Jack Colvin and James Ingersoll portrayed father and son. In reality, Colvin was only 14 years older than Ingersoll.
Jack Colvin appeared in the series as three different characters - Ed Jasper in "Look Alike" (S2E17), Will Collins in "Hocus-Focus" (S3E15), and Dr. Charles Leith in two "Dark Side of the Moon" episodes (S5E8, E9).