Lulu suggests the reason she and Frankie couldn't be frozen by Piper is because they're ghosts, however this alone is not a sufficient reason because Piper has frozen a ghost before.
At 23:15, the instructor is reading a passage about the Magna Carta off the back of an Algebra textbook.
Frankie & Lulu's unfinished business is matrimonial - they wanted to get married. When they robbed the jewelry store they only took an engagement ring ait would have made more sense to get a wedding ring - or even a whole wedding set (one engagement ring plus his & hers wedding rings).
When Paige is in her room looking around you can very clearly see a "Bride of Chucky" Tiffany doll. Paige's parents were killed in 1994 but the movie had not come out till 1998.
There is a Scream poster over Paige's bed. Her parents were killed in 1994, but the movie had not come out till 1996.
There was a Load poster and a Garage Inc. poster in Paige's room, when Metallica didn't release Load until June 4, 1996, and Garage Inc. wasn't released until November 24, 1998.
When Paige's car is hot and it flips over the wig off the mother's dummy flies off.