Grim & Evil (2001)

Fiend is Like Friend Without the 'R' - S1-E4

Continuity mistake: Mandy hits a baseball with one of Grim's bones, yet when we see Grim, there are none of his bones missing from his body.

Show generally

Continuity mistake: In the "Chocolate Sailor", when they get into the boat, Billy is chocolate, and then the next shot he is normal, and the next shot he is chocolate again.

Little Rock of Horror / Dream a Little Dream - S1-E13

Continuity mistake: In Dream a Little Dream when it shows Grim, Billy and Mandy eating the pizza, the box is empty. But when they wake up, there is one slice left.

Fiend is Like Friend Without the 'R' - S1-E4

Trivia: Nergal is the villain introduced in this episode. "Nergal" originally was the name of the Babylonian God of Fire and Guardian of the Underworld. In the Bible, he is one of the demons allied with Satan himself. In the series Nergal is associated with the underworld and fire.

A Grim Surprise / Beast and Barbarians - S1-E9

Trivia: In "A Grim Surprise" when Billy and Grim are in the closet, and Billy is telling Grim about throwing Mandy a surprise birthday party, if you look closely at the boxes behind them, one of them has the word "die" written on it. (00:09:20)

Hoss Delgado: Give it to us straight, Goodburger. Is our little Remus.
Mandy: Billy.
Hoss Delgado: ...Billy, on the bullet train to Smartsville, or is he riding the slow pony to the rubber forest?

Billy's Mom: Oh sorry, Billy. We weren't laughing AT you, we were laughing with you.
Billy's Dad: I was laughing AT you.

Hector Con Carne: I'm not even on this stupid show any more.