Heading down the rabbit hole…
Qwikiverse maps the references between stories: what Six Feet Under nods to, and what nods back. How it works
Wikipedia: Six Feet Under (TV series)
http://www.artofthetitle.com/title/six-feet-under/
Fair use
Nothing spotted here yet.
A line quoted, a cameo, a character named after something: if Six Feet Under nods to another story, or another story nods to it, spot the first one.