She had the fire that he never really saw before...
The way she talked about taking their friend back from those traitorous friends - former friends - of his, it was interesting. It didn't matter to her that they were World Government agents. It didn't matter that they had power that was leaps and bounds stronger than theirs. It didn't matter that they were leaving on a train to Enies Lobby in the middle of the worst Aqua Laguna he had ever seen. It didn't matter that she came close to dying in that Aqua Laguna. All that mattered was getting Nico Robin back to their crew of misfit pirates. (She had said the most when it came to his prudish attitude. She was on a mission to save her crewmate; the way she dressed wasn't one of her concerns!)
She had the iciness he never really felt before...
The way she looked at him when he said to wait until the morning to go after CP9 made his blood freeze. It was such a cold, harsh look, he didn't know if he ever received one like it before. Even Lucci's glares - both pre and post finding out his true identity - couldn't rival the one she gave him. The proposal had the heavy suggestion of leaving Robin to her own devices and leaving her to go behind the Gates of Justice, never to be seen again. There was absolutely no way any of the Straw Hats were going to let that happen. (The look she gave him when he made a comment about her clothes made him feel like he was hit by Aqua Laguna.)
She had the shock factor he never really knew before…
The fact she ran down the stairs to the back alleys and ran over the tops of buildings to save her captain shocked him. Was she really so selfless that she was willing to die with her captain rather than go on without him? (And that reindeer, was he just as crazy as her?) And the fact she was - along with her crewmates - willing to take a ship out into that terrible storm as though it was nothing, it shocked him. Were they idiots? Or were they just that great of friends? (And the fact she changed her clothes right in front of everyone in the train car shocked him as though he was hit by lightning. Was she really so brazen and shameless that she didn't care that these men saw her with barely any clothes on?)
Paulie loves her courage and brashness.
Paulie loves how cold and sharp she can be.
Paulie loves how she doesn't care what people think of her.
(Paulie still wants to tell Nami off about the way she's dressed.)