Corncornos is a brand of corn chips sold in Gravity Falls, Oregon.
In "Irrational Treasure," Dipper and Mabel Pines are first seen eating them as they are driving through town with Stan Pines. Mabel then puts two on her ears as nacho earrings, claiming she's hilarious, to which Stan replies that is debatable. When Mabel goes on stage during the Pioneer Day opening ceremonies, Pacifica Northwest makes fun of Mabel for wearing the chips as earrings, as well as Mabel's overall silliness, thereby causing her to be embarrassed and leave the site with her brother. As the two talk at the statue of Nathaniel Northwest, Mabel talks about how Pacifica is always putting her down and removes her nacho earrings in shame.
Later in "The Deep End," Soos is seen eating them as the Pines family arrive at the Gravity Falls Pool. They are also shown drifting in the pool after Mabel drives away in the Mystery Cart with Mermando in a cooler. One unfortunate kid trapped in "solitary confinement" is seen eating them as they drift close to him.
In "Fixin' It with Soos: Cuckoo Clock," Mabel is seen eating Corncornos.
The bag is yellow with a red triangle (with a white line inside) on the top half of it with the word "Corncornos" appearing in blue and white on it. The chips themselves are triangle-shaped yellow/orange nachos.