A.N. Syaoran the Water Kitsune asked me to do: 'a quiet, watchful drunk who's always making remarks on the things and people near him'. Well Zoro doesn't make any remarks in here, well actually there isn't any conversation in here, sooo, yea…
Quiet, Watchful Drunk
When Luffy met Zoro they didn't have any drinking parties 'cause it was just the two of them, when Nami and Usopp joined they were simply too busy to organize anything. But then Sanji joined and their small company gained their own, almost personal chef, then things changed a little. They started to have their own parties, of course only Usopp and Luffy looked like the ones partying. But they didn't care about what other people though as long as their friends were having a good time. Nami and Zoro were simply sitting and watching the idiot duo. Sanji barely ever drank anything stronger than wine 'cause he was a lightweight.
Everyone assumed that Zoro was the same as Nami and didn't get drunk or hangover at all and as the person who organizes everything (that would be Luffy, he actually has great organizing skills) would be feeling sick the next day no one knew if Zoro had hangover… And as he never complained about having one everyone assumed that he's a lucky bastard with immunity to alcohol, simple as that.
Then things started to change. Sanji started to ignore Zoro and if he didn't he would be harsh and angry. The poor green haired man became confused and hurt. It lasted until Chopper joined. The little man was so sweet that the mood in the crew changed 180 degrees. Of course to celebrate their new member Luffy threw a party. For most of it Zoro simply sat at the bar drinking one drink after another and sulking, that is until he suddenly stood up, grabbed Sanji and dragged the blonde out of bar.
There weren't any news from the two for about a day, but then they were found. By Luffy, doing… Well doing what people in relationships usually do or that is how Luffy explained it to the other when they asked what he saw. Next day both of them showed up with red faces and visible bite marks on their necks. No one was so stupid and no one in any way misunderstood that.
Chopper, who had only been with them for several days, didn't really understood why everyone were so shocked. In his personal opinion the two of them matched perfectly. The relationship between the two of them didn't change much only their bickering became gentler and sometimes ended with sweet words or even kisses. At first everyone found the sudden change very weird, but they only needed to see happy grins the two of them wore and they immediately faced it as their new routine.
Of course everyone wondered why Luffy came across them doing 'stuff' if they left almost 24 hours earlier. Sanji told them everything while laughing. 'The idiot Marimo was actually wasted and as soon as he announced that he's in love with me, he fell asleep while sitting!'
That way Zoro's drinking secret was revealed. He actually was one of those people who once got drunk would start thinking about serious stuff. After every party Zoro would have such big hangover that he would sleep for nearly 16 hours and then wake up without any affects, only a little bit sleepy.