I know the invitation was to share "enhanced" versions of the "Happy Birthday" song as above, but I'm aware of other running jokes of adding lines to things and thought I'd run through a few:
The "...between the sheets" mentioned by Martha added to hymns is familiar to me as a tag for fortune cookies. Someone opens the cookie, reads "Through adversity comes prosperity" and someone else adds "between the sheets".
Don Albert's Dixieland band recorded a version of "The Sheik of Araby" where every line of the lyric is answered by the band "...with no pants on!"
And let's not forget the Simpsons' classic take on "Rudolph the Red-Nosed Reindeer".
5-year-old: Rudolph's nose is red, right?
Me: Yeppers
5: What color are the noses of the other reindeer?
Me: Sorta brown
5: I know why.
Me: How's that?
5: Rudolph flies in front.
Me: And?
5: Santa makes a lot of sudden stops on all those rooftops.
Me: (gobsmacked)
[1980s+; fr gob,''mouth,''and smacked, ''hit, struck,'' the theatrical gesture of clapping a hand over the mouth as a gesture of extreme surprise]
As used today, I think of someone "catching flies" because he has no response, rather than someone clapping a hand over his mouth.
Ron Draney said: The “…between the sheets” mentioned by Martha added to hymns is familiar to me as a tag for fortune cookies. Someone opens the cookie, reads “Through adversity comes prosperity” and someone else adds “between the sheets”.
We did something like that back in the 60s with the titles of popular songs (usually rock). The results were equally amusing. Some examples: I want to Hold Your Hand, I Can't Get No Satisfaction, Foxey Lady, Light My Fire, Touch Me, etc.
I guess another form of the same thing would be the fad a couple of years ago of answering "that's what she said" to every remark that could even remotely be considered suggestive.
Ron Draney quoted: "That's what she said"
I coulda' sworn that was a line used by Dick Martin on Laugh-In. Sounds really familiar, but I couldn't find it here.