Smartest Dog in the World is an episode from the third season of The Garfield Show.
Odie becomes super smart due to intervention from Mrs. Cauldron.
Mrs. Cauldron is brewing a potion when she realizes someone is watching her so she introduces herself and starts telling a story. One day, she was heading back home on her brand new flying vaccuum cleaner when Garfield was currently pulling a prank on Odie, who flies into the air, passing Mrs. Cauldron and lands in a mud puddle. She thought that Garfield was a good cat, but there were times when he misbehaved such as today. She knows that Odie is dumb, so she casts a spell on Odie to make him smarter so events like that will not happen again.
Garfield gets surprised when Odie walks in, talking about Newton's third law of motion. After that, he goes and fixes Mrs. Cauldron's vaccuum cleaner's GPS. Mrs. Cauldron then tells Odie to never tell anyone that she cast the spell on him; otherwise he would have the spell removed and once again become dumb. Odie complies, and Mrs. Cauldron heads back to her home.
For a while Mrs. Cauldron thinks that making Odie smart was a good thing, such as when he helps Jon do his taxes. Jon, perplexed, faints when Odie mentions that he also got him a refund.
Jon takes Odie to Liz, where she finds out that he was two times smarter than both Jon and Liz combined. Jon goes home and starts filming videos of Odie performing very hard tasks for a dog, and because of this, he instantly becomes famous as the smartest dog in the world, even beating the world chess champion and winning money at a game show.
Mrs. Cauldron then says that King Glorm and his fellow Sloth Peoples living inside the earth were worried that Odie was smart enough to conquer the Sloth People, so he makes a plan to capture him so that he could use Odie to conquer the humans.
Back on the surface, people make requests for Odie to solve their problems, and so does Garfield, complaining that he did not actually have a part in the episode. Odie goes out to solve both of their problems, while Garfield drove off everyone.
Odie went to the park, avoiding many people who wanted him to do stuff for them. He relaxes for a second as there no one in the park at that time, until the Sloth People drilled out of the earth and took Odie hostage. King Glorm then questions Odie on how he got so smart. He realizes that life before him becoming smart was much easier, then remembers Mrs. Cauldron telling him to never say anything about the spell cast on him. Odie tells King Glorm how he became smart, transformed back into his dumb self. Realizing Odie's actual level of intelligence, King Glorm and the Sloth People head back underground.
Odie heads home, and everything goes back to normal, with Garfield getting his show back.