In Harry Potter and the Chamber of Secrets, before Harry gets sucked into Tom Riddle’s diary, he’s in a candle lit room. When he’s in the diary, everything is in black and white yet, we can still se the candle light flickering on his body.
1
In Harry Potter And The Sorcerer's Stone, you can see a portrait of Anne Boleyn hanging in the staircase. Anne, a wife of Henry VIII, was accused of being a witch and subsequently executed.
2
In the Harry Potter films, Voldemorts’ robes faded in color every time a horcurx was destroyed, to give the impression he was slowly fading away.
3
In Harry Potter and the Order of the Phoenix, Harry wears button down sweaters at DADA meetings similar to what Professor Lupin would wear. This was Daniel Radcliffe’s idea as he thought Harry would want to emulate his favorite DADA teacher.
4
In The Goblet of Fire, a reflection of Nagini slithering can be seen in the Warner Bros. logo.
5
In Prisoner of Azkaban, Newt Scamander appears on the Marauder’s Map.
6
In Order of the Phoenix there’s a Wizarding world version of Cheerios called Cheeri-Owls.
7
The title of the second film in the Fantastic Beasts Franchise, The Crimes of Grindelwald”, contain the the Deathly Hallows.
8
Snape’s first encounter with Harry and his secret message.
9
In The Sorcerer’s Stone, you can see McGonagall’s name on the quidditch trophy right next to James Potter.
10
Harry Potter intros become darker every time, just like the movies.
11
In The Sorcerer’s Stone scene where Neville gets a Remembrall, he can’t remember what he’s forgotten - but it’s probably his robe, as he’s the only one not wearing one.
12
The ways Harry, Ron, and Hermione wear their scarves and ties reflect their personalities.
13
In The Half-Blood Prince, when we see Tom Riddle’s childhood bedroom there are seven rocks on the windowsill in that bedroom, foreshadowing Riddle splitting his soul into seven horcruxes.
14
In Harry Potter and the Deathly Hallows, Part 2, Snape is still helping the order of the Phoenix when he re-directs McGonagall’s spells to his fellow Death Eaters.
15
In the background of the cafe in Deathly Hallows, Part 1, there’s a poster for the play “Equus” - a real play that starred Daniel Radcliffe and Richard Griffiths.
16
Hermione’s hair grows throughout Deathly Hallows, Part 1, to show how long she, Ron, and Harry have been traveling in search of horcruxes.
17
In the Chamber of Secrets, you can spot Gilderoy Lockhart’s second wig on his desk.
18
The end credits of Goblet of Fire features this disclaimer: “No dragons were harmed in the making of this movie.”