Even if you consider yourself a movie buff, we all miss some things the first time we watch our favorite films.
Whether it's a visual joke that's only on-screen for a few moments, or a tiny detail you wouldn't notice unless you watched the movie over and over, filmmakers love to hide little Easter Eggs in their work.
Test yourself by reading this list of 13 of our favorite hidden jokes, details and references and see how many you already knew.
1. Jurassic Park gives its plot away
Jurassic Park isn't famous for its complicated plot, it's just a fun movie about dinosaurs trashing a theme park, but there is a twist partway through when the scientists discover the park's female dinosaurs can mate.
But if you're paying attention this is revealed at the start of the movie: during the helicopter ride to the park, Sam Neil's seat belt has two "female" connectors, but he makes it work by tying them together. "Life finds a way!"
2. There's a joke hiding in the credits for Frozen
We're sorry for reminding you about Disney's smash hit animated musical, because the songs are bound to be stuck in your head all day now.
But even if you know every word to "Let It Go" you probably never noticed the secret in this movie's credits: a clever joke about Kristof and his claim that all men eat their boogers. Blech!
3. Fun with time travel in Back to the Future
Another "blink and you'll miss it" joke, this one is hiding in the classic 80s comedy Back to the Future. At the start of the movie, Marty meets the Professor at the Twin Pines Mall.
But after running over a tree in the 1950s, Marty returns to the present for the film's finale at the Lone Pine Mall. Get it?
Click the next page for more movie secrets, including Star Wars and Harry Potter!
4. Harry Potter and the Ginger Witch
Who's your favorite character from the Harry Potter series? Ron? Hermione? How about the Ginger Witch? You may not recognize this character, but she's appeared in 4 of the Potter movies including Fantastic Beasts and Where to Find Them.
Her adventures are hidden in newspaper headlines from the movies, but they include stealing a wig and causing a public disturbance involving flying pigs.
5. Steven Spielberg loves a good Star Wars joke
It's no secret that directors Steven Spielberg and George Lucas are good friends, and they've hidden lots of references to each other's movies in their work.
Spielberg has featured Star Wars cranky robots R2 D2 and C3PO in Raiders of the Lost Ark, and Yoda made a special appearance in ET. But Lucas paid his friend back, with a group of ET aliens in Star Wars Episode I.
Maybe this means someday we'll get a crossover movie, with Indiana Jones fighting space aliens!
6. There's something hidden in every scene of Fight Club
This darkly funny movie from the '90s poked fun at businesses like Ikea and Starbucks, including a very subtle joke about how common the coffee shop is.
According to the director David Fincher, you can spot a Starbucks coffee cup hiding in every scene of the movie - except the scene where a coffee shop is destroyed, apparently that was too much for the brand.
7. A hidden message in Saving Private Ryan
During this World War 2 movie's opening scene, the American soldiers shoot two surrendering soldiers. While they're speaking German, if you know the language you can hear them saying something that totally changes the scene:
"Please don't shoot me! I am not German, I am Czech, I didn't kill anyone! I am Czech!" Oops, turns out they were probably prisoners in the wrong place at the wrong time.
8. The secret message in Godzilla
The opening credits of the giant lizard's latest movie featured some sinister-looking military documents with the critical information blacked out.
But if you pause the film, you'll see that lots of the hidden messages are jokes about the film's crew.
Click the next page for even more secrets, including Toy Story and The Matrix!
9. Hidden "glitches" in The Matrix
Strange sightings and deja vu are supposed to be common in the computer-generated world of the Matrix, but did you know sharp-eyed viewers can spot them too?
During Neo's training, the simulated city he walks through is full of twins, a hint that things aren't as real as they seem. The crew flew in real twins from across Australia to pull off this scene. How many pairs can you spot?
10. A naughty secret in The Prisoner of Azkaban
In the third Harry Potter movie, the boy wizard gets the Marauder's Map, which shows the location of wizards throughout Hogwarts.
But fans spotted an unusual pair of feet that seem to be up to no good during the film's credits.
11. Alfred Hitchcock's many cameos
Hitchcock was a director known for two things: his suspenseful films, and his love for clever cameos.
The director would hide himself in his films, sometimes multiple times in one film, appearing 39 times altogether.
His most creative cameo? Sneaking into Lifeboat as a before-and-after ad for a weight loss product.
12. Anchorman's Mexican restaurant
Where does Will Ferrell's hilarious newscaster Ron Burgundy go for a nice meal? His favorite restaurant: Escupimos en su Alimento.
Which, of course, is Spanish for "we spit in your food."
13. All of Pixar's hidden Easter Eggs
There are enough hidden jokes, visual gags and references in Pixar movies to make another list, but this video does a great job of breaking down everything you probably missed.
Share this list if you learned something new!