He was voiced by Christopher Niosi.
Ernesto first appeared in "Let's Be Friends" where two of him were hanging out at the water dispenser while Boxman was carrying Darrell's head. Ernesto was then talking to Boxman about the plaza before Boxman throws Darrel's head in the furnace and replaces him with a new Darrell.
In "Stop Attacking the Plaza" Ernesto just comes home to read the newspaper. Ernesto then attends dinner with Boxman, Darrell, Shannon, Raymond, and Jethro. He and his siblings try to help Boxman take his mind of attacking the plaza, but he just leaves instead. At the end, Ernesto his happy to see that Boxman has gotten through the day without attacking the plaza, just as Boxman presses the attack button.
In "The Power is Yours", Ernesto is seen checking Boxmore's nuclear waste storage pipes before having the entire top half of his body melted off by the waste.
He then appears in "RMS and Brandon's First Episode" where he is attacking the plaza for the first time with his siblings. He fights K.O., Rad and Enid until he is defeated with the rest of his siblings.
He appears near the end of "Lad and Logic" as a baby version of himself along with Darrell, Shannon and Jethro.
Ernesto appears in "OK Dendy Let's be K.O." where he attacks the plaza for the first time. He tries to prepare himself with note cards but fails, until Dendy gives him some constructive criticism which motivates him to fight like himself. He fights Rad, Enid and Dendy by rolling up into a ball then splitting himself into two half's. Enid tries fighting his legs while Rad fights his arms. Dendy then defeats Ernesto by fighting in a holographic K.O. body and punches him back to Boxmore.
In "You're In Control" Ernesto is seen watching Boxman Jr. fight T.K.O, then attending his funeral after his defeat. In "Lord Cowboy Darrell" Ernesto is seen watching Darrel run Boxmore then doing paper work when Lord Boxman knocks it all down. In "Let's Watch the Boxmore Show" Ernesto along with Shannon, Raymond and Jethro compete in Darrel's many challenges just to become senior deputy. Ernesto is last seen going into the furnace and melting after being tricked by K.O.
Ernesto appears in "The So-Badical" as the main antagonist. He gives out multiple Boxmore school books and passes them off as Booksmore school books. He then become K.O. and Dendy's substitute teacher after Miss Quantum goes on sabbatical and starts turning the students' brains into puddings by teaching them boring math problems. In the end, he is defeated and Miss Quantum goes back to teaching.
- Before "ARMS and Brandon's First Episode", Ernesto was the only robot that hadn't attacked Lakewood Plaza Turbo yet.
- He is the biggest of Lord Boxman's children.