This seems to work from a double mis-aiming:
This one got a chuckle from Chemgal. While not really a CIDU, it does have me scratching my head to see if I can remember where “There can only be one” could come from. Oh, you say there are multiple sources? No, but there can only …
Thanks to Rob for this Stahler:
And Rob steps right back in with this 1-and-done:
Comics I Don't Understand 
The source I know is the “Highlander” series
What is that green blob hanging from Hip Girlfriend’s nose? Snot? Gigantic piercing jewelry? Maybe a huge button on the couch?
It’s a nose ring.
But “My girlfriend’s hip” is something no one would ever say unironically in said girlfriend’s presence, would they?
For a moment, I felt nothing at the Pharmacy one. Then a laugh came out of me that the whole house could hear.
The grampa/girlfriend one strikes me so odd, that I almost feel like I’m missing something, but it doesn’t seem like a hip enough cartoon for that, and so I’m left with thinking that the author is just so unhip that his attempt to come up with a “kids and their bizarre slang” so badly misfires that he uses a “hip” term that has easily been “in the know” cool-slang for at least as long as anyone has been alive today — even if you were born in the 1910s or aughts, you were alive and young during the roaring 20s, which is the first time I’d say hip/hep got popularized, and it just kept on, peaking again in the 60s/70s (most of the 60s happened in the 70s), and just never going away. OK, maybe grampa was/is a square, but that doesn’t hinge on his age, it could have been anyone who is unhip to hip…
The “corrected the grammar” one is something I’ve threatened to do repeatedly. I’m astounded at the number of folks who send computer-printed Christmas letters that haven’t even been spellchecked, much less read by a native speaker of English*.
A shorthand some friends and I use when copyediting is to mark something NQE–Not Quite English–to indicate “Whatever this sentence is supposed to be saying, it doesn’t succeed”. All too often appropriate.
Merry Christmsa**, eh?
*Not talking about letters sent by non-native speakers here.
**Deliberate–see https://en.wikipedia.org/wiki/Muphry%27s_law
larK, I agree there is something amiss or opaque about the generation-gap one. But I don’t read it as you do in some details. I thought that “hip” was not meant as the younger guy’s normal expression, but something he is picking out with the idea it will speak to his Grandpa. The old guy’s misunderstanding of “hip” as a noun is probably meant just as it appears, that he is unfamiliar with the slightly slangish use of “hip” — which I agree is not really plausible, since it’s been around for a long time and has not really gone away. But what else could it be? Somehow a jab at the grandson, for trying too hard?
I’m not really getting what’s going on with the plunger-yielding archer.
Whenever someone has said ‘You’re back!” (i.e. “you have returned.”) to me, I’ve sometimes responded, “What a bout it? (i,e. “What about my back?”) just to mess with them. And somehow it all seems less amusing now that I just typed it all out.
The “hip” comic may be somewhat clunky, but it still seems to work for me.
That Kliban one is just so weird I’m not sure what to make of it.
I liked the swans.
Reply All never seems to do anything for me, ever.
Don’t get the first one at all. Any significance to the navigation light colours of her rings?
Grawlix and Mike P, yeah, Reply All is generally very subdued humor. What strikes me as funny here is just that she picks this kind of not life-changing detail to bring up with the therapist as theoretically or in-principle potentially life-changing.
1 – “My girlfriend’s hip…” Grandfather used to dealing with older people – especially women – is wondering what is wrong the girlfriend’s hip. As in “My girlfriend’s hip has been hurting her terribly this week.” While grandson means “My girlfriend is hip.”
2 – Yes, it is the HIghlander (movies and TV series) in which “there can be only one”. At the end of the first movie the Highlander, Connor McLeod wins the fight with the last other immortal and he is now “the one” and gets a normal lifetime and then he will die instead of living forever. Somehow in the TV series his younger cousin Duncan McLeod is the Highlander (and in some episodes Connor, played by same actor as in the movie, is also featured). It is never explained how he exists and his cousin is back and alive – but good TV show anyway.
The idea is that at the end of the fighting among all the “immortals” over the centuries there will be only one left alive and he/she will live for one lifetime as a regular person before dying.
(Wow – my brain has not turned to mush after the last few crazy weeks.)
Oh, and in the movie and TV show “Highlander” – the fighting between the immortals is done with swords.