On the show "Rick and Morty", in episode "Total Rickall", who was a parasite?

In the episode "Total Rickall" of the show Rick and Morty, Pencilvester is revealed to be a parasite rather than a real character. Initially appearing as a beloved family friend, it is ultimately exposed as a deceptive being that creates false memories and emotions. This is evident when Rick mentions that it is a parasite capable of disguising itself as a loving and nostalgic creature, preying on the minds of the hosts.