Right now, there are scenes with the kobold mage, the bat, and the shark
For the kobold you need to compliment his muscles while you are small and his picture is at least at the second stage. You can also get more stuff with him if you wear the Wizard Hat that you can get from the cobra.
You can find the bat and the shark at the pier's bulletin board at night. To get the scene with them at least one of them has to be interested in you. To do that you can either flirt with the shark in battle and then apologize, or you can talk to the bat about something he's interested in and when he's at stage 3 tell him you don't want to fight him.
After you do that you can get scenes with them individually by repeating the things that make them interested in you.