In the episode "Ferekh", Apple and Onion watch after a chicken named Ferekh that scientists want because it remains young so has the cure for aging. Apple and Onion age to elderly, while a security cop is turned into a baby because the actual source is a green soup like food it is fed.

We learn the reason is all the years are transfered to a single part of the body. The baby security office has an elderly hand, and a news reporter who appears a kid has an elderly foot

https://www.wcostream.com/apple-onion-season-2-episode-7-ferekh