He is almost always mad or angry. He enjoys making up riddles for visitors who try to cross his bridge. However, he is shown to be happy at times and does have a few hobbies.
The Grumpy Old Troll is mostly yellow. He has a long orange beard and an orange mustache. He has white eyes with black pupils. He does not wear any clothing at all.
Grumpy Old Troll appeared in some episodes of Dora the Explorer. His first appearance was at the ending of "Beaches".
- Season 1 - Surprise!, Bouncing Ball, Backpack, Little Star, Call Me Mr. Riddles
- Season 2 - The Happy Old Troll, To the Monkey Bars
- Season 3 - The Fix-it Machine, The Super Silly Fiesta, Louder!
- Season 4 - The Shy Rainbow, Dora's World Adventure
- Season 5 - Dora's Christmas Carol Adventure
- Season 6 - The Grumpy Old Troll Gets Married, Dora in Troll Land, Halloween Parade
- Season 7 - Perrito's Big Surprise
- Season 9 - Max and Ruby. The Flintstones.
- Grumpy Old Troll tends to be grumpy most of the time. In season one, whenever the troll sees Dora and Boots solve his riddles, he gets angry and lets out steam, or he would stomp his feet. On later episodes, he gets more impressed after Dora & Boots solve his riddles.
- Most of the time, anyone who tries to cross his bridge has to solve a riddle. Sometimes, he gives an instruction or a task to do.
- When Dora and Swiper traveled through time in "Dora's Christmas Carol Adventure", Grumpy Old Troll had no mustache and no beard when he was a baby.
- The Grumpy Old Troll and his wife Petunia appear in the Dora and Friends episode, "Return to the Rainforest".