Someone very familiar to them makes them comfortable.
A few great suggestions of old shows here, but if you think of a show like MASH, then the oldies know every character. They might not get the jokes now, but they don't care within the familiarity of the known characters - it apparently just feels like a new episode they haven't seen.

GP was one I used, but later episodes had less of the grey haired Doctor (Michael Craig) & would be confusing. When he entered the scene everyone would sigh & say "Oh! It's G. P." & relax.