Regarding Chip Davis, according to his funeral he was Duffman from '92-'96 and '08. Given it has already been established that multiple people have played Duffman, it works. By that logic, Chip appeared as Duffman BEFORE we first saw the character in the series (Duffman first appeared in "The City of New York vs. Homer Simpson" which was in '97). The only episode to feature Duffman in 2008, according to The Simpsons wikis, is "Homer and Lisa Exchange Cross Words". So Chip Davis was Duffman who in turn was in a relationship with Grady:
http://simpsons.wikia.com/wiki/Grady
A Brief History of the Men Who Played Duffman:
Pre-1992: unknown
1992-1996 - Chip Davis - unseen in the series
1997 - unknown, could be Larry - first appearance in the series
2000 - Larry - Moe slaps a sticker on his face which causes him to pass out or die (Pygmoelian)
2001 - Sid - may have died of liver failure (Hungry Hungry Homer)
2002 - unknown - Lenny mentions the previous Duffman (Sid?) died of liver failure and this Duffman is his replacement (Jaws Wired Shut)
2002 - unknown - pledges his love to Lunchlady Doris after being shot (The Great Louse Detective)
2003 - Barry - could have replaced the previous Duffman who died from being shot or is the same Duffman as seen in 2002 (Old Yeller-Belly)
2007 - unknown, dating Boobarella (Homerazzi)
2008 - Chip reprises role - Chip is gay and in a relationship with Grady (Homer and Lisa Exchange Cross Words)
2009-present - unknown
I also liked The Simpsons Movie callback as well as the town hall meeting attendee credit. Makes me wonder if Chip is actually a background character that the animators have used in the past.
So, despite being a nobody, he actually is sort of a known character if you consider him a former Duffman and Grady's lover.
edit: wait, what the fuck? the broadcast version had yellow text credits and an Edna memorial, while the Hulu version has a Chip Davis memorial as well as doctored images of Chip in various past episodes:
http://imgur.com/a/TBYOc
As much as I loved the Edna tribute, the addition of the Chip ending actually pays the gag off and explains why Joe Nameth was at his funeral. I like how some of the scenes have him hidden because of the 4:3 ratio.