The three test subject zombie heads that Odegard and Murphy inject with Batch 47 resemble Moe (Moe Howard), Larry (Larry Fine), and Curly (Curly Howard). Also known as The Three Stooges (2000). Curly head played by Foy Gene Spencer.
At one point in the episode, Doc says "It's like one big shop of horrors!". This is a reference to the musical "Little Shop of Horrors", which is about a giant plant that eats people.
Just before entering the greenhouse Murphy says "I love the smell of zombies in the morning." This is a reference to Robert Duvall's quote "I love the smell of napalm in the morning" from the 1979 film Apocalypse Now.