It’s exactly what the title suggests. Listen here.
Most of his songs are either originals or parodies, but this is neither–just a genuine cover/compilation.
My wife is an enormous Hamilton fan. I like it well enough, but prefer Weird Al.
I played this track at 6:40 this morning, before she’d had time to assemble a caffeine shield against horror. Her one comment was, “I…I can’t unhear that, can I?”
I think I’m pleased.
Doesn’t he do a polka compilation in every album?
Yes, he does, and he also does numerous style parodies, where he imitates the style of a specific group without parodying any of their songs.
Jimmy Fallon made sure Lin-Manuel Miranda was on camera when he heard it for the first time. Looks like he loved it. Lin-Manuel Miranda and Jimmy Fallon React to Weird Al's "Hamilton Polka" - YouTube
He does a polka compilation on every album; I think there’s precisely one album in his catalog without one. I think he said somewhere that if he didn’t do one, there would be rioting in the streets. (Note, that’s what he said, I’m fairly sure it was a joke and he didn’t literally think that.)
Two albums, his first and fifth(Even Worse).
Just got back from Al’s show at Foxwoods. It’s a new format, no more costumes and videos and dancing around, mostly originals, not parodies. They played a couple parodies, but the first song of the encore was a straight up cover, no parody, no polka: I Saw Her Standing There. They sounded great, he has a very talented band and this format really lets them all shine.
Can’t wait to see him in Portsmouth NH again tomorrow. 
Each show’s a bit different, too.
He mentioned the Hamilton polka tonight, but said it was too complex for them to play live.
So Polka is the ancestor of Rap?
Better than the original score!
NItpick: Not compilation. Medley. A compilation is a collection of previously released songs, like a greatest hits album.
List of “Weird Al” Yankovic polka medleys
I was gonna nitpick you and point out that “Bohemian Polka,” from Alapalooza, is a single song and not a medley, but “Yankovic’s official website has categorized ‘Bohemian Polka’ as a polka medley.”
There’s still another album without a polka medley if you count Peter & the Wolf.