Continuity mistake: When the bartender fills up the mug with root beer, the foam has instantly settled when the shot changes.
Continuity mistake: In the beginning of the show, Cory is showing Shawn something he wrote in the school paper. Cory walks away leaving his backpack on the bench. In this whole scene to the point where Cory says, "Is it just me or is it just me" sometimes he is wearing his backpack, and sometimes he isn't. (00:00:20 - 00:03:05)
Continuity mistake: When Alan is saying "It's a miracle bra, honey, get a camera," his left hand is resting on the table. When the shot changes, his left hand is suddenly resting on his right arm. (00:08:00)
A Long Walk To Pittsburgh (1) - S4-E16
Continuity mistake: After Cory finishes downing his soda, he places the cup on the table. When the shot changes, his hand is instantly away from the cup. (00:16:37)
A Long Walk To Pittsburgh (1) - S4-E16
Character mistake: After learning that Topanga will be moving to Pittsburgh, Cory tries to rationalize their desire to be together for the rest of their lives despite still being so young by comparing their relationship to that of Romeo and Juliet, thinking they turned out OK. Shortly thereafter, he is shown reading the book in his backyard and explains the situation to Mr. Feeny, who advises him to skip to the end to find out what happens to their relationship, much to Cory's dismay. The problem is that Cory already learned the fate of Romeo and Juliet in Mr. Feeny's class in the first episode of the series. He was even dismissive over the idea of a man killing himself over a woman.
A Long Walk To Pittsburgh (2) - S4-E17
Continuity mistake: When Topanga comes back to see Cory, for the whole period of time that she is there, sometimes her hair is dry and straight, and others it's wet and wavy. (00:07:12 - 00:21:16)
A Long Walk To Pittsburgh (2) - S4-E17
Character mistake: In this episode Cory says that Topanga gave him his first kiss at age 13, but their first kiss actually happened when they were 11, in the 6th grade. (Season 1 - Episode 7 Cory's Alternative Friends).
A Long Walk To Pittsburgh (2) - S4-E17
Continuity mistake: After Cory finishes explaining to Amy why he loves Topanga, he sits down next to her and begins placing his arm around her. When the shot changes, his hand is instantly resting on her shoulder.
Other mistake: When Eric and the other security guard discover Mr. Feeny entering the school, Feeny expresses that Eric snuck up on him. Eric was five feet away from Feeny when he first saw him, and was also talking loudly when making his approach towards him. There's no way Feeny couldn't have heard him.
Continuity mistake: When Amy is trying to get Alan to back off Mr. Mack, the way her hand is gripping his arm changes between shots. (00:16:45)
Character mistake: When Cory is telling Shawn that he has a lot of questions about The Centre, Shawn invites him to check it out sometime. A couple scenes later when Cory does just that, an incredulous and defensive Shawn asks him why he is there, as if he forgot he invited Cory to check the place out.
Visible crew/equipment: When Eric jumps out of his chair and exclaims "No" during his college acceptance interview, a boom mic can be seen being pulled out of view. (00:19:00)
Revealing mistake: While the girl who just broke up with her boyfriend is on the phone with the ex, she is throwing his stuff out the window. As she throws the last couple of CDs out the window, you can see the backdrop of the beach sway a little bit.
Revealing mistake: You can tell the ocean visible from the dorm room window is just a backdrop, as there are no waves approaching the shoreline.
Answer: I learned the answer to this one today. It is "Tree of Life" by Garé Barks.
Phaneron ★