- While all of his songs are funny, not to mention incredibly quotable, his live albums include a few moments that have the audience laughing so hard that Lehrer actually has to stop and wait for them to calm down. Most infamously, from Bright College Days:
Lehrer: Soon we'll be out, amid the cold world's strife/Soon we'll be sliding down the razor blade of life...
Audience: [loses it]
Audience: [loses it again]
- There's also his announcing of the song Oedipus Rex, which involves a lead-up of him describing how motion pictures have songs released with them. He then starts talking about the recently-released movie of Oedipus Rex, and then says "This film was not a financial success, and I believe this is because -". He got that far before everyone burst out laughing, at which point he said "You're way ahead of me on this one".
- In the introduction of "The Irish Ballad": "As you know, audience participation is an important part of public folk singing, so if any of you feel like joining in on this song, I would appreciate it if you'd get out."
- The introduction to "We Will All Go Together When We Go" has Lehrer recount a novel a friend of his wrote, "about a young necrophiliac who finally achieved his boyhood ambition by becoming coroner." This only drew a few chuckles, but his next line brought the house down: "The rest of you can look it up when you get home."
- "The Masochism Tango", which includes the words "Fracture my spine, and swear that you're mine, as we dance to the masochism tango"
- Lehrer's appearance in the Cameron Mackintosh tribute concert "Hey Mr Producer". He makes his entrance at the piano, on a moving platform. When it comes to a stop, he remarks "they promised me seatbelts". He then credits himself for Mackintosh's success, saying "the combined profits of Cats and Tomfoolery" made Cameron into the man he is today". When talking about Mackintosh's rags-to-riches story, he said "even then, he had exquisite taste in rags". He then goes on to perform Poisoning Pigeons in the Park, to an audience that includes the Queen of England.
- The Irish Ballad, about a girl who murders her family:
"And when at last the police came by
Her little pranks she did not deny
To do so she would have had to lie
And lying she knew was a sin."
- Most of In Old Mexico, but especially:
The mariachis would serenade
And they would not shut up 'til they were paid
- The Vatican Rag. For example:
Get in line in that processional
Step into that small confessional
There the guy who's got religion'll
Tell you if your sin's original.
- Also, the introduction - "I have here a modest example..." Tom Lehrer has never provided a "modest" example of anything in his life and his audience knows it.
- Heck, the audience goes to pieces the very instance he announces the title!
- From "Lobachevsky":
"I am never forget the day I am given first original paper to write. It was on analytic and algebraic topology of locally Euclidean metrization of infinitely differentiable Riemannian manifold; боже мой! ...This I know, from nothing."