The Stanley Brothers’ A Life of Sorrow is a sequel to Man of Constant Sorrow—the latter of which, of course, was made popular in the movie O Brother Where Art Thou?.
Bananas At Large
Da Turdy Point Buck and Da Turdy Point Buck II.
Second Week Of Deer Camp
snork
Best of the Worst indeed! 
I came here to mention that. It sucked.
The novelty C.B. song *Convoy * had a sequel, about the rogue truckers travelling around the world by driving on water, thanks to the faith of the Jesus freaks in the convoy.
Either that, or I took more drugs in the seventies than I remember.
The Twist - Chubby Checker
Let’s Twist Again (Like we did last Summer) - Chubby Checker
'Round The World With The Rubber Duck.
Shep & The Limelites “Daddy’s Home” can be seen as a sequel to their earlier “A Thousand Miles Away”.
It was real!
Thanks, Johnny.
Fred Jones part II - Ben Folds
The first one was Cigarette
Also Paul Simon’s The Boxer part II, Still Boxing
The Killers have the murder trilogy, though the first part of the trilogy is an unreleased song.
First, “Leave the Bourbon On the Shelf.” Supposedly, this is about the narrator hearing rumors of his girlfriend cheating on him, but I’ve never heard the song or been able to find the lyrics to it.
Then, “Midnight Show.” The narrator apparently kills his girlfriend over his belief that she’s cheating on him.
And finally, “Jenny Was a Friend of Mine,” which is apparently the narrator rehearsing what he’s going to say to the police.
I hadn’t been aware that it was a series of songs at first and just thought, geez, the lead singer is twisted. How many songs about killing your girlfriend can one guy write? Apparently, a whole bunch if it’s the same girlfriend. :dubious:
Now how do you feel about that? Better that it’s real? Or worse that it wasn’t the drugs? 
“Snoopy’s Christmas” was the second sequel to “Snoopy vs. the Red Baron.” The first one was “The Return of the Red Baron.”
Oh Pearl Jam has a few, I think. Why Go is supposed to precede Daughter, and Once, Alive, and Footsteps are supposed to be a trilogy.
This combines the idea of a sequel and an “answer record”, which was sometimes a sequel, and sometimes the same song with the lyrics changed to reflect a different point of view.
Aretha Franklin’s “Respect” is an answer record to Otis Redding’s earlier original version.
Sample Otis lyric:
Do me wrong
Honey if you wanna
You can do me wrong Honey while I am gone
Corresponding Aretha lyric:
I ain’t gonna do you wrong while you’re gone
Ain’t gonna do you wrong 'cause I don’t wanna
Neil Sedaka once did a song called “Oh Carol”.
Carole KIng then recorded a song called “Oh Neil”.
In a similar vein, after David Bowie released his “Low” album, Nick Lowe released an EP called “Bowi”.
The album-side-length “Hemispheres” by Rush is subtitled “Cygnus X-1 BookII”.
I seem to recall a perfectly awful sequel to the Steve Lawrence hit Go Away Little Girl called I Won’t Go Away Little Boy. Couldn’t begin to tell you the name of the girl who sang it, though.
I don’t know if this is really a sequel or not. The Police did a newer version of “Don’t Stand So Close to Me”, which is titled “Don’t Stand So Close to Me '86”. According to the lyrics sites I checked, the lyrics for each version are the same.
I keep coming back to “What do we mean by sequel?”
Locomotive Breath could be considered the sequel to Auqalung and almost every record Savatage issued was an opera with sequel following sequel to the end of the story.
“Destroyer” by the Kinks referrenced “Lola” in its lyrics and “Hello I Love You Won’t You Tell Me Your Name” in the guitar work.
There was a third sequel, Snoopy For President, in 1968.
*
Waiting at the pumpkin patch, a dog sincere and brave
And everybody hoped that soon the country he would save
The pumpkin said “The day has come for you to take a stand”
“For love has left the people across our native land”
Some wear the sign of the elephant
and some wear the sign of the mule
But we’ll hold the sign of the beagle high
and love will shine right through*