The brief 'Happy Anniversary' scene
This one really got to me (in a good way!) and for multiple reasons:
Firstly, Bub adding the romantic lights and playing the classic Lady and the Tramp love song
Secondly, their different expressions / reactions to the song being played for them
Thirdly, Nibbles’ sly laidback grin in the background, and near the end, we see her also going along with the music.
All of those thing are great. But there’s one that REALLY sold it for me:
How both Judy and Nick simply went along with it.
One or both of them could’ve tried to say, ‘oh, no, it’s not that kind of anniversary’ or ‘this isn’t necessary, shut that off’. But neither said a single word.
Based on Nick and Judy’s typical interactions/disagreements, I’d expect Judy to brush it off or give him some over-cheery goofy grin while Nick would pointedly glare at her or make a sarcastic comment/joke. Perfect examples: the ‘eating worms’ scene, or literally seconds before the anniversary scene when he said 'thank you for this':
But instead, Judy gives him this awkward nervous side glance like ‘oh shoot, what is he going to think of this’, while Nick looks stunned for a long period of time before finally glaring straight ahead and not meeting her eyes at all.
And keep in mind at the beginning of the movie they literally pretended to be a married couple with a child and there was no awkwardness about it, so a fake anniversary blurb is pretty minor.
HOWEVER: that was a deliberate act to expose a criminal, where this was a misunderstanding they were not prepared for. Also, Judy already said 'happy anniversary' twice to Nick and he was chill -- because no one else reacted, so he could brush it off as just their silly banter.
At Nick’s apartment, Judy says ‘no one will question whether you and I belong together’, instead of just ‘whether you and I should be partners’ or ‘whether you and I belong on the ZPD’.
When the goats say ‘have fun at the Honeymoon Lodge’, Nick yells a sarcastic ‘thank you’ at them before making the same expression. At no point did Judy mention why she and Nick were going to the lodge, the goats only saw a pair wanting to go to the Honeymoon Lodge. Again, another sudden misunderstanding that hit too close to home for Nick. Sure, one could argue he was just annoyed that Judy was going to listen to him and leave town until the goats intervened, but the wording seems too intentional (they could’ve said ‘good luck don’t fall off the cliff’ or ‘don’t get bitten by a snake’ rather than ‘have fun’)
My personal opinion: at this point, Nick didn’t fully realize his feelings for her have gotten deeper because he’s used to ignoring his emotions, but I think these scenes stirred something inside him that he wasn’t eager to deal with, especially considering he and Judy weren’t getting along well at these points.