Ricky is putting on a new Gay Nineties revue down at the club, and Lucy begs to be a part of it. She says that, once the baby is born, she will be busy taking care of it and not be able to be in showbusiness anymore. She tells Ricky that she wants to perform one last time before the baby is born, as a sort of "showbiz swan song." Ricky does need a fourth person to join the barbershop quartet number he, Fred, and Ethel are going to be a part of, so he has Lucy practice singing "Sweet Adeline" with them all. Naturally, Lucy can't keep the tune to save her life, and Ricky, Fred, and Ethel end up sneaking out and leaving Lucy alone. To get revenge, Lucy calls up the person Ricky was originally going to have be the fourth barbershop quartet member, and she sneaks into the number by playing the customer in the barber chair, her face hidden with towels. When Ricky unwraps the towels and finds Lucy in the chair, Lucy immediately tries to sing along. But her attempts are thwarted by Ricky, Fred, and Ethel all sticking their shaving cream-filled brushes into her mouth. Lucy has the last word when she jerks to make the other three all get their brushes stuck in THEIR mouths.
- Lucy and Ethel end up singing "By the Light of the Silvery Moon" for their audition, once Lucy found the old hoop skirt to use as a way to hide her pregnancy. She originally wanted to wear a barrel and sing "Roll Out the Barrel," but Ethel told her that isn't a Gay Nineties song.
- George Watson was supposed to be the fourth member of the barbershop quartet.
- For some reason, this episode ran too short. So, Desi hired his good friend Pepito the Clown to come and do some tricks, like riding the "world's smallest bicycle," to fill up the extra time, which was edited in to the episode after filming. Pepito appeared in the pilot, and he was supposed to reprise his role in the pilot for "The Audition." He wasn't available at that time, though, so Buffo the Clown was used instead. But most of Pepito's act in the pilot is reprised here in "Swan Song." Both acts are identical, minus the lion trainer bit in this episode, which wasn't in the pilot. Even the "Fascinating Rhythm"-sounding instrumental music that plays while Pepito undresses and reveals his oversized wristwatch is exactly the same in the pilot and in this episode.
- Ricky's attempt at an Irish accent was (of course) horrible. The only words he says with somewhat of an Irish brogue are "same," "name," and "time."
- The story goes that William Frawley was really angered with the script having Lucy sing "Sweet Adeline" terribly and off-key. Even though her awful singing made the episode funny, Frawley couldn't bear to hear a song he considered so lovely and classic to be butchered. He said that Lucy's off-key singing sounded like "sh*t on baked Alaska."
- As with every other episode where Lucy had to sing off-key, Lucille Ball purposely hit the wrong notes. In real life, she could actually carry a tune quite well.
- When this episode originally aired, during the end commercial, Alfred Lyons, head of Phillip Morris basically said that I Love Lucy could be canceled if viewers didn't buy more of their cigarettes.
- Parts of the barbershop quartet finale in this episode were used as "flashbacks" in the 1956 Christmas special.
- If you look closely during Lucy and Ethel's number, you can see Lucy discreetly pull a string on her skirt, which made the pantaloons fall down.
- Lucy misses her final singing cue right before she and Vivian start dancing. Vivian points at her to remind her to sing.
- The first time Lucy wants to get back into the act after having the baby (in "The Indian Show"), Ricky's main argument is that Lucy's primary job now is to take care of the baby, reminding her how the performance in this episode was supposed to be her showbiz swan song.
- Ricky: You know, we didn't have the Gay Nineties in Cuba like you did over here. What were they like, Fred?
Fred: I don't know. That was before my time. Ask Ethel!
- Lucy: (singing) I was strollin' in the park one day, in the merry, merry month of May. I was taken by surprise by a pair of roguish eyes...
Ricky: (singing) And you can put that parasol away! Bum-bum!
- Lucy: (to Ricky) Would you begrudge an expectant swan her song?
- Ethel: What number are you gonna do [in your barrel costume]?
Lucy: Oh, I never thought about that. I could sing "Roll Out the Barrel."
Ethel: You could, but it's not a Gay Nineties song.
Lucy: Oh. How 'bout "Put on Your Old Gray Barrel"? "I'm Only a Bird in a Gilded..." No?
Lucy: (shows off her pregnant stomach) Well, that should be fairly obvious!
- Ethel: But why can't YOU be the man?
- Lucy: I am NOT mad.
Ethel: Well, then you've got a new way of acting happy!
- Ricky: (to Lucy) But there is no room for a Gay Nineties striptease!
- Ricky: (to Lucy) Oh, you're a sorehead.
Ethel: Oh, now, Ricky, it's her condition.
Lucy: It is NOT my condition! I was a sorehead long before I ever thought about having a baby!
- Lucy: (singing) Goodnight, ladies! Goodnight, ladies!
- Ricky: We're singing "Sweet Adeline." We're singing harmony. Everybody's singing something different.
Lucy: Well, then, that's just perfect. If everybody's singing something different, it won't matter what note I hit!