So far, there are 7 scenes that I could find:
(extra lines to spoiler it for those who want to figure it out themself)
1. Use Allure Potion on Vine
2. Use Allure Potion on Vine after... either increasing Lewd rating or unlocking Elasticity Elixer (not sure what unlocked the alternate scene)
3. Use Allure Potion on Slime
4. Use Allure Potion on Slime after... either increasing Lewd rating or unlocking Elasticity Elixer (not sure what unlocked the alternate scene)
5. Talk about Allure Potion with Philia (the goblin), come back at Night
6. Talk about Elasticity Elixer with Jessica (the merchant), come back at Night
7. Talk about Elasticity Elixer with Beth (the minotaur), come back at Night
The four Slime and Vine each have alternate versions for doing them again. The Philia/Jessica/Beth scenes clearly are intended to have alternate versions as well, but those presumably aren't made yet.
Haven't found any way to do anything with Alo'Eth (the drow librarian); I would guess that will require something found in the First Wing of the library, which hasn't been made yet.