When this was new, in 1965 or 1966 (I can’t quite make the date out — though the 6/16 at lower left is quite clear, as the pigeons have not yet picked it up), probably it was already a challenge to the reader to recognize some already-retro references, to famous real-world couples or other cartoon-world characters. And probably some randomly tossed-in names; and probably some not-famous real-world friends of Mort Walker’s; and certainly some pairing-up jokes (Emmy and Oscar?).
And after the passage of another 55 or 56 years, how many of them can we get? I’m not really much of a comics historian, so maybe … none? But others may do better.
Comics I Don't Understand 
For what it’s worth, the date is 1965. Many of the names certainly sound like they could be old-time cartoonists and their spouses, and the many dates (years only, never a specific day, unlike real life graffiti) are certainly suggestive of references to actual married couples. However, I don’t recognize any of the pairings, and examples you might expect to be there are missing (e.g., no Bil + Thel, no M.W. + J.S. (Jean Suffill, Mort’s wife at the time)).
Little did Killer know that he would lose out for Miss Buxley’s affections to Beetle. My theory is that she suffers from crippling low-self-esteem, and never believed any of the guys who gave her compliments and such. Beetle treats her as she thinks she deserves, with near indifference.
Is that Miss Buxley or Jen Erica?
This strip predates the introduction of Miss Buxley, so it isn’t her.
As far as I can tell, I recognize Mort Walker’s siganture.
Wait, “Walt and Connie” are the parents in Zits, but that’s anachronistic. Bob and Ginny would be Robert and Virginia Heinlein, at least for me.
As far as I can tell, I recognize Mort Walker’s sigantureYes, an interesting bit of contextualizing. If the signature is going to be there anyway, does putting it among the graffiti make it something internal to the story?
Walt and Connie anachronistic? It looks like it says 1992, which really would be anachronistic. (I’m sure it is actually 1942.)
If the names and initials are not just completely random, I think they might be Walker’s personal friends, although the wide range of dates would seem to rule out any relationship to birth and/or anniversary years.
P.S. Killer’s date seems to bear a significant similarity to the future Mrs. Flagston. It doesn’t seem all that improbable that he might have dated Beetle’s sister Lois.
There may be a real-life Walt & Connie that both Mort Walker and the Zits creators paid homage to.