Board Thread:Questions and Answers/@comment-7371650-20160705050546/@comment-27701762-20160705062500

The only secret thing is pouring water on Undyne. Everything else can be done at any time in the run so long as the basic guidlines are met. You could, for instance, go through the entire game on your second run, then go back and befriend Papyrus, Undyne, and Alphys. The only secret thing about Alphys is that you can't befriend her until after you've completed a Neutral run (which I presume you already know).

Papyrus's date/hang out can be completed in any way you choose. It doesn't really matter, except insofar as his responses change.

If I might make a suggestion, you should make your first playthrough to get a feel for it, and then do your second playthrough. If things seem to be going wrong (i.e. you can't trigger the event befriend Alphys), then come back here and either look through the Wiki page, or ask on the forums for help and we'll be able to direct you. The game doesn't really have any obtuse puzzle logic, so you shouldn't fear losing huge amounts of time in doing one particular thing wrong.