Lenny's Japanese name is Ren and Morty's Japanese name is Manta.
Lyserg Diethel and his poppy fairy Morphine are both named after drugs. Morphine's name is obvious and Lyserg Deithel is short for Lysergic Acid Diethylamide.
Rio's Japanese name is Ryu and/or a.k.a Bukoto no Ryu (Ryu of the Wooden Sword).
The Minutians are actually called the Koropokkurs.
There were plans for a continuation for the anime but the creator turned it down due to the fact that they were not allowed to use the original sound track,