A rejuvenation clinic was where the physical effects of old age could be reversed, adding "30 or 40 years" to a subject's life and making them appear proportionately younger. Emmett Brown underwent the process at either age 65 or 71, some time between his departure from 1985 and his later return, possibly in 2015 — though likely even further into the future. (See Behind the scenes: Actuality below.) Doc thought he looked so youthful that he then added prosthetic age makeup before returning to 1985 so that Marty McFly would be able to recognize him, which he peeled off after the DeLorean time machine had landed in the alleyway.