Not a joke, this irritates me like almost nothing else.
One of my favourite musicians of all time is Meat Loaf (also not a joke). He has stacks of excellent songs, including "I'd Do Anything For Love (But I Won't Do That)", about a dude who is in love and claims he would do anything for love, but in the chorus he admits that actually, he wouldn't do "that". It's pretty well known and often referenced in popular culture, e.g. in Spice World The Movie where he plays the tour bus driver who, when asked to fix a clogged toilet on the bus, answers "I'd do anything for those girls, but I won't do that".
Anyway, the one thing about this song that I don't love is the fact that for some reason, 90% of people think that the thing Meat Loaf won't do is a big mysterious secret, and the remaining 10% think they have it figured out but actually don't.
I am here to let you in on the secret: the thing Meat Loaf won't do is EXACTLY WHAT HE SAYS IN THE SONG. Throughout the song, he lists a bunch of things he would do for love, juxtaposed against things that he definitely wouldn't do. In English, the word "that" is used to indicate a person, thing, idea etc as physically pointed out or, in Meat Loaf's case, verbally mentioned. So when he says he won't do "that", he means he won't do "the thing we were just talking about, like literally two seconds ago, honestly what is your problem".
And I would do anything for love, and I'll be there 'til the final act
And I would do anything for love, and I'll take a vow and seal a pact
But I'll never forgive myself if we don't go all the way tonight
And I would do anything for love, oh I would do anything for love
I would do anything for love, but I won't do that*
(*I won't forgive myself if we don’t go all the way tonight)
Toward the end a lady joins Meat Loaf and asks whether he'd do a few things, e.g.:
Will you raise me up? Will you help me down?
Will you get me right out of this godforsaken town?
Will you make it all a little less cold?
To which Meat Loaf replies:
I can do that.
Then she gets cynical and suggests that things will change one day:
I know the territory, I've been around
It'll all turn to dust and we'll all fall down
Sooner or later you'll be screwing around
And he protests:
I won't do that.
This is the one part of the song that some people are able to comprehend, so the few who don't think "that" is a big secret think that the thing he won't do is cheat on her. Which it is, in this particular verse. Just not for the entire song.
I really don't see why this is so hard to understand in the first place but if you're a person who just doesn't get demonstrative pronouns, here's a handy list that you can print out and keep in your wallet to avoid getting on my last nerve in the future: