To get the rest of the scenes...
- Have a good relationship with Toriel. E.g. don't snoop in her diary, don't spy on her in the bath, be kind to her, etc. And once under the effect of the monster food, let her nurse you.
- To get the rest of the scenes: During your first dinner with Toriel, ask about other humans, and then ask about the last human. Later, you will get the choice to either go to the Markets, or another place. Choose the other place.