WARNING: The following article contains spoilers for Fantastic Beasts: The Crimes of Grindelwald, in theaters now.
Set decades before the birth of Harry Potter, and months after the events of 2016's Fantastic Beasts and Where to Find Them, director David Yates' Fantastic Beasts: The Crimes of Grindelwald features significantly more nods to the main series than its predecessor did, including several blink-and-you-miss-them references.
While the inclusion of Albus Dumbledore and Hogwarts School of Witchcraft and Wizardry are too prominent to be considered Easter eggs, and several familiar spells and enchantments are too numerous and obvious, the following is a list of the film's more subtle connections to the Harry Potter series:
In the prologue, Gellert Grindelwald (Johnny Depp) is led from his holding cell in New York City to a convoy to take him back to Europe to answer for his crimes. The stagecoach Grindelwald is confined to before he stages his daring escape is drawn by black, leathery creatures known as thestrals.
Introduced in Harry Potter and the Order of the Phoenix, the winged beasts are invisible to all but those who have witnessed death firsthand. After watching Cedric Diggory's murder at the hands of Peter Pettigrew in the climax of Harry Potter and the Goblet of Fire, Harry is able to see that Hogwarts' carriages, which he previously thought were propelled by magic, are actually drawn by thestrals.
The Cursed Snake
First shown as a prisoner of the Circus Arcanus in Paris, a young woman named Nagini (Claudia Kim) possesses the ability to transform into a giant serpent. The circus master notes the woman is originally from Indonesia, and the blood curse that allows the transformation will eventually leave her permanently trapped in snake form.
Nagini is Voldemort's trusted snake familiar with whom he shares a special telepathic link, and can command completely under his will. First seen in The Goblet of Fire, the snake is later revealed to be a Horcrux containing a piece of Voldemort's soul, and rarely leaves its master's side. Responsible for the death of Severus Snape, Nagini is ultimately decapitated by Neville Longbottom in the climactic battle of Harry Potter and the Deathly Hallows.
Seen sporadically over the course of the film through various magical tools and remedies, a young, blond-haired man with heterochromatic eyes is revealed to be a decades-younger vision of Gellert Grindelwald.
While the inclusion of a young Grindelwald may not necessarily be an Easter egg in and of itself, the casting of the actor for the role certainly is. Jamie Campbell Bower reprises his role as the young Grindelwald after portraying the character in flashbacks in Harry Potter and the Death Hallows - Part 1; he's the only cast member thus to appear in both the prequels and the main series as the same character. As the decision to depict Grindelwald as heterochromatic was suggested by Depp in for Fantastic Beasts and Where to Find Them, this is the first time Bower's incarnation of the character is depicted with different-colored eyes.
Newt Scamander (Eddie Redmayne) and Leta Lestrange (Zoë Kravitz) are shown in a flashback sequence learning how to confront boggarts under the instruction of Hogwarts Defense Against the Dark Arts Professor Albus Dumbledore. Taking the form of their respective greatest fears, Dumbledore instructs his students to see beyond the illusion and use a defensive charm to defeat the beast.
The lesson, and use of boggarts, mirrors a similar lesson led by Professor Remus Lupin for Harry Potter and his friends in Harry Potter and the Prisoner of Azkaban.
The Young McGonagall
Albus Dumbledore is not the only professor from the Harry Potter series depicted in The Crimes of Grindelwald, nor is he the only professor from the House of Gryffindor. After weeks of rumors and speculation, a young Minerva McGonagall, portrayed by Fiona Glascott, does indeed show up as a professor at Hogwarts, albeit in a relatively small role here.
While there has been debate whether McGonagall would be old enough to be a professor at the time of The Crimes of Grindelwald, her appearance is a welcome, if chronologically unexpected, face in the crowd.
The Mirror of Erised
After being confronted by authorities from the Ministry of Magic, Dumbledore retreats into a private chamber, where he uncovers a large, dusty mirror. The looking glass displays the professor as a younger man with a young Grindelwald before showing Dumbledore at his current age, reunited with Depp's incarnation of the character.
First seen in Harry Potter and Sorcerer's Stone, the Mirror of Erised shows users their heart's greatest desire; Erised is "desire" spelled backward. The mirror is later seen in flashbacks in Harry Potter and the Order of the Phoenix and Harry Potter and the Half-Blood Prince, while it makes a small appearance in Harry Potter and the Deathly Hallows - Part 2 in the Room of Requirement.
When Dumbledore gives Newt his new mission to travel to Paris and track down Credence Barebone (Ezra Miller), he provides him with the address to a safe house in the city belonging to an old friend. While taking refuge there much later in the film, Jacob discovers how literal "old friend" means when he comes face to face with its ancient owner, Nicolas Flamel, portrayed by Brontis Jodorowsky.
Flamel as introduced off-page, and off-screen, in Harry Potter and the Sorcerer's Stone. The magical alchemist created the titular stone to grant himself and his wife immortality, and entrusts the object to Dumbledore to keep it safe from Voldemort's followers, who seek to resurrect their dark master. When Flamel leaves his home to save the day in the finale, he opens a safe where the Sorcerer's Stone can be briefly seen floating inside.
Lestrange Family Tree
Hinted at with a photo and passing dialogue in Fantastic Beasts and Where to Find Them, Leta Lestrange (Zoë Kravitz) makes her full debut here, with much of the film exploring the Lestrange family history. As Lestrange debunks Credence Barebone's suspicion that he is a long-lost half-brother to her and Yusuf Kama, she shows Credence an enchanted family tree of her family proving her baby brother to be dead.
The glimpse at Leta's extended family offers a look at the background of future Harry Potter villain Bellatrix Lestrange. Originally a relative of Harry's godfather Sirius Black, Bellatrix would marry into the Lestrange family decades later combining the two pure-blooded magical lineages.
The Order of the Phoenix
Over the course of the film, Credence Barebone is seen caring for a young, sickly chick. After Grindelwald reveals to his new protege that he is actually Aurelius Dumbledore, the chick suddenly transforms into a majestic phoenix, the mythical bird that will appear to Dumbledore family members at their moments of great need.
The phoenix is most likely Fawkes, who debuted in Harry Potter and the Chamber of Secrets in Dumbledore's office long after the venerable professor became Hogwarts' headmaster. Reborn in a continuous cycle after molting in a fiery display, the bird eventually comes to Harry's aid by the story's climax. While it is unknown if Credence's phoenix is Fawkes, the Dumbledore family connection makes it likely.
In theaters now, Fantastic Beasts: The Crimes of Grindelwald is directed by David Yates from a script by J.K. Rowling. The film stars Eddie Redmayne, Jude Law, Johnny Depp, Katherine Waterston, Alison Sudol, Dan Fogler, Ezra Miller, Zoë Kravitz, Fiona Glascott, and Callum Turner.