- There's a shot of Bigfoot◊ in the opening credits. Blink and you'll miss it.
- The last frame of the opening sequence depicts Bill Cipher◊ surrounded by a ring with symbols on it. These symbols have been seen on or near various important characters on the show, and Bill refers to some characters as their associated symbols (most frequently, he calls Dipper "Pine Tree"). All of this hints at some sort of prophecy involving them all, with Bill connecting them together. The prophecy isn't explained until the final episode of the series.
- At the end of the opening credits, you see a page from the journal with the words "VWDQ LV QRW ZKDW KH VHHPV". When decoded it reads "STAN IS NOT WHAT HE SEEMS".
- The journals have a lot of these, in the forms of foreshadowing, creepy info about the local monsters, and the occasional joke.
- "Knock! Knock! Who's there? THE FORCES OF EVIL!"
- Dipper's list of suspects from "Headhunters" is in full: Manley [sic] Dan, Old Man McGucket, That Fat Guy, Angry Lady, Mikey R., Uncle Phil, Susie.
- Blendin Blandin, the time traveler from Episode 9, can briefly be seen in the first◊ three◊ episodes◊, fixing the paradoxes the twins caused.
- Episode 16- Pause right when Stan opens the book to the page about the pituitary gland, and you'll find a Caesarnote cipher at the bottom: "SXEHUWB LV WKH JOHDWHVW PBVWHUB RI DOO. DOVR: JR RXWVLGH DQG PDNH IULHQGV" (PUBERTY IS THE GREATEST MYSTERY OF ALL. ALSO: GO OUTSIDE AND MAKE FRIENDS).
- In "Dreamscaperers," Bill Cipher does this twice.
- When he says "I know lots of things. Loooots of thiiiings." his triangle flashes countless images, and if you pause them you can see, in that order: John F. Kennedy (implying something), blurry UFOs, Mayan scriptures, one of Journal 3, the moon landing, one of the pages of the journal, a skull with a cigarette, Stonehenge, the Pyramids, Stan going for his secret vending machine door, the Sasquatch seen in the opening, another page of the book, Crop Circles, the secret room where the twins found Quentin Trembley, a statue of Nathaniel Northwest, part of the stamp on the postcard from the intro, various clocks, what seems to be a abandoned warehouse, a maximum security prison, then it repeats the blurry UFOs and the blank scriptures.
- When Gideon mentions Stanford Pines, Bill flashes the symbol from the Universe Portal's console that's burned onto Stan's back while trying to recall him.
- When Dipper phases through the floor in "Sock Opera" you can see a box with an antenna and the government agency's symbol on it. Later, Agents Powers and Trigger can be seen in seated in the audience at Mabel's show hiding behind newspapers.
- During the second "Mabel's Guide to Life" short "Mabel's Guide to Stickers," Mabel holds up a book of myths. In the Aztec portion of the book there is an Aztec retelling of the Air Bud franchise.
- When flipping through the journal to find out how to defeat a catagory 10 ghost, a shot of a 'catagory 9' ghost can be seen, AKA a 'Dream Hipster' which "turns power naps into horror naps". The hipster itself bears a strong resemblance to Freddy Kreuger, with a bottle opener, fork, knife, and spoon instead of normal blades.
- During "Weirdmageddon 3", after Dipper and Mabel are captured by Bill and taken back to Stan and Ford, look carefully at "Stan's" hands on the cage: he has six fingers, revealing that Stan and Ford pulled a Twin Switch while Bill was busy chasing the kids.
- There's also a classified document that's shown onscreen in the episode "Irrational Treasure" — it's a biography of a character on the show. The characters who discover it glance over it briefly and then say the important information out loud, but if you pause (or read really quickly), you'll find that the document includes the paragraph: "Let it be here recorded
Nathaniel Northwest, famous in his native Gravity Falls for standing in the park and hitting himself with a large boating oar until he blacked out, was chosen to be the patsy mayor of Gravity Falls. Northwest spoke in a series of grunts and screams and often yelled his trademark phrase: "I am going to eat this entire oak tree because I am a powerful wizard!""
- It also had some Foreshadowing for the next episode:
- As well as some Breaking the Fourth Wall (the brackets are part of the quote):Writing jokes for cartoons is more important than sleep.If you recite the pledge of allegiance backwards, you'll gain secret wizard powers! (This one works, kids! Try it at home!)
- In "Not What He Seems", an old newspaper article is shown briefly, and much like the classified document about Nathaniel Northwest, the characters read the important part out loud. If you pause when it's onscreen, though, you'll notice that it suddenly changes subject towards the end: "In other news, leg warmers are all the rage this week and we predict this style will go on forever."
- In "The Last Mabelcorn", Dipper gets hooked up to a machine that can display his thoughts. When this happens, a large amount of text appears on the screen, going by very quickly. It includes some nods to previous episodes, among other things.
Freeze Frame Bonus / Gravity Falls