The hit animated TV series "Hey Arnold!" was supposed to end with a movie called "Hey Arnold! The Jungle Movie" in which Arnold, Gerald, and Helga go on a quest to find Arnold’s parents.

For those of you who don’t remember, Arnold (aka: Football Head) was a fourth grader who lived with his grandparents in the city of Hillwood. In each episode, Arnold and his friends went on hilarious misadventures; often learning about themselves and each other along the way. 

But Arnold’s world was pulled off the air after the 100th episode, in which his Grandpa’s car is stolen and it’s up to Arnold to solve the case. Originally however, the finale was meant to be as epic as the entire series itself. According to creator Criag Bartlett and various other sources, Arnold and his classmates were meant to go to San Lorenzo in Central America after Arnold wins them an essay contest. 

Once there, Arnold, Gerald, and Helga were meant to look for Arnold’s parents with the help of the mysterious Green-Eyed People; a tribal society who his parents were helping. The villain of the movie was supposed to be a disguised treasure hunter and river pirate named La Sombra. The movie was cancelled due to the poor ratings received by the previous Hey Arnold! Movie. 

(Source)