This episode has multiple Disney references. Ash continues to compare heaven to Disney World and the Magic Kingdom. The two hunters who kill Sam and Dean are named Walt and Roy (Walt Disney's brother's name is Roy).
Zachariah says that in Heaven he has 4 faces one of which was a lion, this would make him a Chebrium. In the Christian Angelic Hierarchy it is the Chebrium's job to guard the way to The Garden of Eden as well as God's Throne, which is exactly what he is doing when he stops Sam and Dean from entering the garden.
Ash tells Sam and Dean, "Most people can't leave their own private Idaho." He is referring to the 1991 River Phoenix cult classic My Own Private Idaho and the 1980 hit song on which its title is based, "Your Own Private Idaho," by the B-52's.
During one of Dean's memories of being a kid, Mary asks him if he wants some pie. The implication being that his long standing affection for pie is rooted in associating it with his Mom & happier times.