There are some slight innuendos.

In a island a form of a naked woman Is seen briefly

The whole idea that Flapjack is a little kid, and is hanging out with older men can be a little disturbing.

Lots and lots of gruesome slapstick! Kind of like Ren & Stimpy, but add a little bit more gross-out scenes to the mix.

Some character are violent, aggressive and even psychopathic.

Knuckles explodes in one episode. Candy and blood fly everywhere.

Knuckles's head explodes, but it grows back right after we see his head gone.

Flapjack and Knuckles live inside a whale called: Bubbie. Flapjack sometimes plays with Bubbies guts.

Lots of characters look disgusting, with blood, snot and cuts all over their face.

Nothing in particular. Some name calling.

Flapjack and Knuckles eat candy everyday, and it's kind of like a symbolism to drugs, as they look quite high and happy after eating. They also act like complete addicts towards candy.

Some drinking and smoking.

Lots of close-ups of absolutely horrendous looking characters and faces.

Almost everyone looks quite horrific in this show. Also, almost everyone Flapjack, Knuckles and Bubbie come by is a complete nutcase/psycho.

The slapstick can turn rather dark sometimes.

The world in which Flapjack lives looks very grim, evil and dark.

It can get very over-the-top sometimes and the humor is hilarious, so those scenes can lighten up the mood considerably, but be warned that some scenes can be nightmare inducing.