Continuity mistake: After Kat finds a bedroom for herself, the long sheer white curtain hanging near the framed photo of Amelia repeatedly changes between pulled open or closed; particularly noticeable when Kat dumps her clothes from the black trash bag and tosses a ball of socks into Casper's mouth. (00:25:15)
Deliberate mistake: After James and Kat enter Whipstaff and get the power turned on, when Kat heads to the staircase to go search for a bedroom, we can see a few of the metal stair runner rods attached to the stairs to keep the carpet runner in place. However, when James falls at the top of that staircase and gets rolled up in the carpet runner like a sushi, there are zero stair runner rods. (00:21:30 - 00:31:50)
Continuity mistake: Carrigan decides to make Dibs a ghost, so she goes after him with a double-headed axe. Then, when Carrigan slips on the muddy goo, her black pointy toe high heels turn into beige flat rubber-soled shoes, seen in her close-up as her foot lifts up. (01:11:45)
Deliberate mistake: After Stinky delivers his "Smell-o-gram" to James, he trips over the vacuum and falls, then continues down the stairway, with his body rolled up in the stair runner as it gains momentum. The problem is when the sushi runner hits the ground floor, the runner's edge is facing the opposite way to what it should be; deliberately done for the momentum and to have it humorously unroll. It's entirely impossible for it to turn itself around and then still have even more momentum to unroll the way it does. (00:31:45)
Answer: It was not Casper (now a ghost of 12 yr old boy) who wrote there was a hidden treasure at Whipstaff Manor. It was Casper's father, Mr. Mcfadden. The treasure in the box is an autographed baseball which used to belong to Casper, before he got sick and died. Mr. McFadden missed his young son Casper, so he invented a machine that can bring a ghost back to life. He considered Casper's baseball a treasure, because to him it is the greatest treasure there is - the baseball that belonged to his 12 yr old son before he died.
Super Grover ★