The solidly funny reveal of Jon's idea of the relationship intensity-level between attending professional lectures and looking at hosiery is supported in each panel by more-or-less normal interaction turned into comedy mirrors by the various failings and passions of the characters. This is, in the end, a strip about how goofy and bad Jon's taste is, while straight man Liz is wearing a lemon-lime tube top.
1: Jon's sentiment is not unwelcome (Liz returns it), but the thrust of his character is in how he earnestly announces "I like you" as a way to start a conversation. Garfield stands by watching, though he is not usually interested in Jon's doings, which makes us ask: what was going on before this scene?
2: I cannot praise enough, nor do I need to unpack the image of a man announcing "I think it's time we took our relationship to the next level" as he simultaneously makes a mad dash away from a woman. It is maybe not as relevant to Jon and Liz's lives as some other people's, but it is a fine portrait of human romance through the ages.
3: Pointless observation (!): seven bubblettes is a lot of little circles to descend from a thought bubble.
If Polka-Karaoke Night sounds fun to you (it kinda does to me), and/or you don't think polka is inherently funny, you have fallen prey to a trance effecting many Garfield readers. After 27 years, it's easy to forget Garfield is a cat. The joke is that Jon has a designated night that he sings polkas to his cat. Normally he is alone for this, but now that he has a girlfriend, she and Jon get to take turns singing to each other... and the cat. God help me, I want to see the strip where Jon spends hours trying to coax Garfield to do a Frankie Yankovic number.
Unlikely: -That Jon is able to hook up a microphone and amp and lug a full-sized accordion (they're heavy, folks) into the room with enough speed to surprise Liz. This is timing that works pretty well in Bob Clampett cartoons, and can be done in radio, but functions effortlessly in comics.
-That the karaoke festivities require live instruments, which would be more of a "Sing-Along as Jon Plays Accordion Night."
-That Garfield would be so happy about polka karaoke night. Unless he's being sarcastic and/or rubbing it in to Liz that this is what her life has become.
Meanwhile... The Let's Polka blog is incensed over today's strip. Please let this start a war between a polka blog and a Garfield blog: WELCOME TO THE 21ST CENTURY! The critics say Garfield is toothless; I say let 'em eat my big fat hairy deal.