Playing Undertale for the first time!!!

OMG after all these years of procrastinating and putting this off, I'm finally playing Undertale for the first time. Astoundingly, within all that time, I have not come across any spoilers and will be going into the game completely blind. The only two things that I know are that if you kill Toriel, she'll remember even if you restart the game and that Sans and the other skeleton dude are bad guys. I'm so excited because I've heard how good this game is. Wish me luck!