Strange, by all means, this shouldn't happen. You said you "can not reliably recreate the sequence" of events? Does this mean it's only happened once? It looks like a command was either run twice or a different one was ignored
Edit: Nvmd. I recreated the bug and I know what happened. It's patched.
So, as it's coded, there are three conditions in order to invite Lucille to the party. They are: you've discovered Lucille's interest in anime, you've established with Peach that you're going to start inviting people and there's an active time limit before the day of the party, and it's evening when you talk to Lucille (That's when she's most willing to talk about anything besides anime.) As for asking Marline about Susie and Susanne; the way it's coded... hmm, yep, that's not right. The way it's coded: if you DON'T ask Susie and Susanne about their milk production before playing the game with them, the option to talk with Marline about them WON'T come up. You could however win against them to clear the condition of there being a challenge, then ask them about their production. The story will look very confusing from there though. If you do this, the option to talk with Marline should come up.
To be precise: some features that have yet to be added to the full game will be a part of the demo after I switch to Beta. But right now the only difference is the available artwork. That won't be made free.
