I think I get now why Punchline#1 mirrored that iconic Joker/Harley cover. It was show the difference in the relationship dynamic.+
First look at Harley's position in this pose it screams submission. She's leaning against him allowing Joker to take her weight basically he's holding her up while she's weak. Her head is tilted towards him and her face is in a blissful smile. +
she's absolutely happy and contented right now. Joker on the other hand is not even paying attention to Harley. He's looking at us. He has a sinister smile on his face as if he's up to something. He's gripping her wrist which, alludes+
to his control over her. He has a possessive hand around her waist. Which shows his ownership he feels over her. This whole image shows the complete Dynamic of their relationship.+
Harley being blissfully unaware and happy and Joker being present but disinterested+
Next let's look at punchline and Joker. Joker grabbed Punchline and immediately put her in the same position as he had Harley. Same controlling hand on the wrist, same possessive hand gripping her waist he's basically turning her into Harley.+
However punchline immediately rejects that. she stabs him. When she stabs him she is basically telling Joker that, no she's not going to be Harley. She's not going to be submissive and their relationship+
is going to be something completely different. This becomes more apparent in the kiss scene. While we don't get to see their full body language like how we do with the Joker/Harley image. we do get to see their facial expressions.+
They're kissing but they're smiling in the kiss like their amused. Like they enjoyed what just happened this whole dynamic switch. Joker is also actively participating. His eyes are closed, he has his hand in punchline hair.+
Now this is important because the act of holding someone's head in a kiss can be interpreted in a few different ways. He could be cradling her head in a loving, soft gesture or pulling her close making the kiss more passionate+
either way it shows a mutual interest. Meanwhile punchline never let go of her knife so she basically showing that she doesn't underestimate the Joker. she knows how dangerous he is. she knows that she has to keep her guard even if she's loyal to him.+
I find that very interesting. I didn't notice at first but after rereading it like three times I think it's really cool.