Specifically in Silver Age ones .
Acually , I don't think The King ever made any appearances , specifically authorized/" as himself " ones in comic books of the Silver Age especially if we restrict this to standard-format " comic books " , as opposed to ~ um , " magazine-format comic books " , where versions/images of The King were frequently seen .
Actually , Don Glut once commented that the plot of " a parody of Frankenstein's Monster that ends with the Monster , having left the Doctor , being shown at the end of the story ass a Elvis-like teenage idol , on stage doing his act with teenage girls expressin g their desire for hioim and throwing stuff at him " ~ was the most-used storyline of all time in MAD-style parody comics ~ and I think Don had a good point !
There was certainly a glut of that storyline (GRROOAN)...
Elvis mostly was shown in parodies, which wasn't hard, given his quirks. If they could do it in a Broadway musical, it was easy to do in a comic and avoid any problems that might arise. MAD was a big fan, as you allude.
It's not that hard to track down The Pelvis' SA appearances, although it's not always easy to figure out his role and whether it was just in a poster or a walk-on, based on the GCD listing. They're not always specific, no doubt because the Indexer doesn't know any more than I do from looking at the cover. I don't know that any were "authorized," per se, but the ones where they used his name and likeness may have been.
For instance, he had a big cover moment and in one of the stories in I Love You #60 from Charlton, but there's no indication of what his role was in the story.
He also appeared in a story in Joe Simon's Going Steady vol. 4 #1 as a character and on the cover. If you're going to use Elvis in a story, you probably put him on the cover.
He also showed up at Patsy Walker's wedding in Patsy Walker #97, along with a bunch of other celebrities, and in Kathy #22 and Career Girl Romances #32.
For some reason, none of these comics seem to be in my collection, which I was shocked--shocked!--to discover. Who knew I had so many holes?
There may be a couple others that I missed, but you can easily check them out by searching for Elvis as a character at the GCD. Then all you have to do is weed through all the times he appeared in an ad for photos of your Favorite 50 Stars, MAD parodies and other chaff.
One of the characters in the 80s DC prestige format series Thriller was a character obviously modelled after Presley called Kane Creole. In fact, there were two Kane Creoles, one modelled after the older Presley and the other after the younger. The elder had been jailed for the murder of his promoters, which act he committed for a reason revealed at the end of #6 (spoiler warning for the link).
I'm a bit surprised that he didn't show up in 50s or early 60s Superman family books because they certainly had the likes of Pat Boone and Perry Como so Elvis would have been a logical step, back in his early days. Maybe they just couldn't get the rights? Or maybe he was just too hip? :)
There was a one-shot in 1957 titled Jughead's Folly where Archie's pal did an Elvis riff for the whole issue. I assume it was a parody, but I've never read the story or stories.
The story is a five-part single story that (spoiler warning!) turns out to be a dream. Jug is dejected because Veronica won't invite him to her party because he's a "nobody," his friends won't pay attention to him, and he can't drown his sorrows in a burger because he's broke.
He sings his blues along with a song on the jukebox, a talent scout signs him and makes him famous, which is only enhanced by his announcement that he hates women. He becomes so famous that he can't go out to get a burger, and his manager won't let him eat one because he's put Jug on a diet.
He sabotages his career and returns to Riverdale broke, which is when he wakes up. He goes to Veronica's party, where a talent scout hears him sing, offers him a contract and we get the usual screaming in terror that shows up in the final panel of a dream story.
This was something of a precursor to the later Jughead's Fantasy, a three-issue series with Juggie in other roles, only the first of which (Juggie in Camelot) was a dream. The others were due to amnesia (detective) and an experiment (super-strength).
Jug was clearly based on Elvis, as were lots of parodies at the time, which makes this a really rare Archie comic, as the combination of sorta-Elvis and Archie made it popular with many collectors.