"Pun Times with Punsie McKale" features a moment where Flapjack finds himself surprisingly holding his own against Punsie McKale in a pun-off....and then Punsie assaults poor Flapjack with a series of color-based puns as he transforms into a hideous rainbow creature that is so intense it causes Flapjack to faint.
Friendly Fandoms: With Chowder, as both shows are centered around excitable young protagonists named after food with older mentor figures, and are often considered to be the highlights of the infamous CN Real era. There's also a little with Sanjay and Craig due to the producer of that show being Thurop Van Orman himself as well as Adventure Time, Gravity Falls, Regular Show and Over the Garden Wall as the creators of those shows all worked on Flapjack before moving on to their own things.
Genius Bonus: The town they live in is called Stormalong Harbor. Stormalong was a tall tale about a giant who became a sea captain.
Dr. Barber's profession. Barbers were often relied upon for medical treatment such as bloodletting (still represented by the red stripe on the barbers pole outside their shops) because they were often the only ones with sharp instruments to hand.
Harsher in Hindsight: With Flapjack's creator and voice actor going on to voice Li'l Gideon, the title character's very behavior and presence has become this.
Idiot Plot: The Termite episode requires you to accept that that K'nuckles forgot that he can take off his legs in order to make any sense. Scratch that, more than half of the episodes require that you accept K'nuckle's lack of understanding of anything to mindblowing extremes. Also Insane Troll Logic is this show's stock in trade.
Memetic Mutation: The scene of Captain K'nuckles being impressed by the dog Colonel doing a backflip has been become a meme, such as it being set to the tune of Shooting Stars.
Captain K'Nuckles. In one episode, his love interest left him because she found him unattractive, when in actual fact he's got a very simple, even cute design -that is aside from the frequent Gross-Up Close-Up which may show what he looks like in-universe.
What an Idiot!: In Gone Wishin, Flapjack tries to stop K'nuckles from spending all his and Flapjack's candy mermaid tears because it was slowly killing a mermaid.
You'd Expect: K'nuckles should have just listened to Flapjack and give the tears back to the mermaid so she would not die.
Instead: He uses the last mermaid tear to wish for a corn dog and a new hat.
As a Result: The mermaid dies from the resulting wish, and becomes a skymaid.
What Do You Mean, It's for Kids?: The series is ostensibly meant for a young audience, and at first glance it really doesn't look like it's not. After a few episodes though, the large quantities of Surreal Horror, graphic Body Horror and dark humor were and still are more than a bit unnerving for its target demographic.