||Overall, while there is no explicit sexual content, romance and puberty are frequently featured themes, and there are some mild sexual jokes.
One of the main protagonists has a hopeless crush on someone much older than him. This is mentioned frequently throughout the series.
One of the main protagonists flirts with and has brief relationships with a variety of boys, one of whom she shares a kiss with ("The Deep End").
Many side characters have romantic relationships as well, but only flirting is shown in lieu of sexual content or nudity.
One character is frequently seen wearing only boxers and an undershirt throughout, in a nonsexual context. Additionally, some male characters are occasionally seen shirtless or in their underwear, again, in a nonsexual context.
Puberty is mentioned throughout. In several episodes, one of the main protagonists insecure about his masculinity deals with issues such as chest hair, voice changes, sweating issues, feeling awkward, etc.
It is implied that some characters have books or magazine with sexual content; this includes characters reading "age-inappropriate" romance novels ("Carpet Diem"), a book about puberty, adult magazines ("Scary-oke"), etc. There is no explicit sexual content in any of these instances; it is only implied in a comedic manner.
There are occasionally some mild sexual jokes, including one about somebody's Internet history being creepy ("Into The Bunker"), and a brief scene of somebody taking a bath with squirrels ("Gideon Rises"). However, these are all brief and subtle.
||Action and fighting is present throughout the show. Cuts and bruises are shown, but there is usually very little blood or gore.
Characters are occasionally eaten whole, but later turn out to be fine. ("Summerween"; "Land Before Swine")
Monsters are occasionally dismembered, crushed, beaten, etc., but do not have any human or red blood or gore. Any monster blood is usually green. ("Scary-oke")
Occasionally, characters can be briefly seen without skin, revealing the flesh, muscles, and bones beneath.
There is some blood, but this is usually shown only very briefly. In "Northwest Mansion Mystery", blood drips out of the mouths of animal heads on the wall, and in "Society of the Blind Eye", through the bandages of a character's injured hand.
In "Northwest Mansion Mystery", a character is killed after being hit on the head with an ax (off-screen).
||Juvenile insults like "poop head" and "dork."
Some religious exclamations.
Instances of "heck."
It is implied that characters make inappropriate hand gestures.
Some teens spray paint words like "McSuckitt" and "weiners." ("Society of the Blind Eye"; "The Golf War")
An incomplete use of "son of a..."
The expletive "flipping" is used once.
||Overall, alcohol, drugs, and smoking are very infrequently mentioned, and mentioned in a comedic manner when they are.
Two underage characters enter a bar with fake IDs ("Headhunters"). This scene is meant to be comedic.
In another comedic scene, a character experiences fantastical hallucinations after consuming outlawed candy. ("The Inconveniencing")
Characters engage in an exchange of fairy dust and butterflies, but the set-up mirrors a drug deal. ("The Last Mabelcorn")
There is only one instance of smoking, where a character is seen with a pipe in one episode. ("Headhunters")
||Mystery and horror are frequently featured throughout the show. Although the horror can be considered relatively mild, many episodes have a lot of suspense.
The protagonists encounter a variety of monsters such as ghosts, zombies, and demons; some of these may be frightening to young children.
There are some scenes meant to shock viewers, such as a scene where blood suddenly drips out of an animal's mouth ("Northwest Mansion Mystery"), a scene where the bodily openings of a character's face are rearranged ("Weirdmaggedon Part 1"), etc. This contributes to the horror element of the show.
There are many emotional and upsetting scenes present. These include two characters discovering that they may not really know their uncle ("Not What He Seems"), a character deciding to stay in the town and not go home with his sibling, causing them to fall out ("Dipper and Mabel vs. The Future", the haunting memories of two characters ("Weirdmaggedon 2: Escape From Reality") and the most emotional of all: a character losing their memories and the two protagonists going home after calling Gravity Falls their home for a matter of months. ("Weirdmaggedon 3: Take Back The Falls").
Northwest Mansion Mystery is a particularly frightening episode.