Celebrity and historical characters heads

On Futurama, some humans are visible as (alive) heads in a jar, most of which can be seen in the Heads Museum.
This technology associated with cloning has made it possible to recreate many historical figures of the 19th and 20th centuries, such as presidents, movie stars or singers.

The technology used to keep the heads alive was invented by Ron Popeil, who himself benefits from this invention.
To be kept alive, the heads are bathed in a liquid containing a tiny quantity of powder made from opals. This creates a temporal stasis, where they are preserved with the same youth as they had in their respective eras.

Ingesting this substance will temporarily send the person who drinks it and those around them back in time to the time period of the head it is preserving.