In this Sabrina is allowed to tell a mortal she's a witch and they can know for 24 hours. She tells Harvey and he still likes her and loves the idea and thinks it is cool she has magic powers. (Also something similar to this happened at the end of season one titled Troll Bride), however at the end of season four titled The End of an Era Harvey finds out that she is a witch and dumps her. Hard.
Beth Brodricks and Melissa Joan Harts heads start to move to the right before the cgi bat flys past them.
Sabrina celebrates her first Friday the 13th as a witch but the year before there were two of them. Also the previous episode was Halloween and Friday the 13th in 1997 happened several months before.
When Sabrina takes Valerie into the classroom to tell her she's a witch, the hallway noise goes away before she even closes the door.