21Beauxbatons girls
In Harry Potter and the Goblet of Fire, when the contestants enter the arena for the third task, the Beauxbatons girls in the audience can be seen dancing the Macarena.
22Hallows Symbol
In Harry Potter and the Goblet of Fire, in the scene with Dumbledore, Harry, and the Pensieve, there is a 3D model of what looks like Hallows Symbol which becomes an important symbol in Harry Potter and the Deathly Hallows. Though the final book was not yet written when this movie came out, J.K. Rowling had a lot of influence over the movie details and she added lots of objects and plots in the movies that were referenced later.
23Weasley family in Egypt
Early in Harry Potter and the Prisoner of Azkaban, Harry sees a newspaper article with a photograph of the Weasley family in Egypt. Though it is never again mentioned in the movie, this is a very important plot point in the book. While on an inspection of Azkaban, the Minister of Magic had a copy of that paper, gave it to Sirius Black, who recognized that Peter Pettigrew was disguised as Scabbers. This is why he decided to break out of Azkaban, track down Scabbers at Hogwarts, and take his revenge by killing him.
24Time-Turner
In Harry Potter and the Prisoner of Azkaban, Hermione can be seen tucking away her Time-Turner early on. Throughout the movie in fact, pretty much anytime someone comments on how she got there or when she isn't wearing her jumper or robe, the Time-Turner is visible around her neck.
25Opal necklace
The opal necklace, which plays an important role in Harry Potter and the Half-Blood Prince, can briefly `be glimpsed in the second movie inside a display case in Borgin and Burkes’ shop in Knockturn Alley when Harry first enters it.
