Donny McStuffins is Doc's 4-year-old younger brother who loves playing with his toys. He doesn't know about Doc's toys coming to life. Donny owns lots of car-related toys and action figures. We learned in "Dusty Bear" that Donny is allergic to dust so he couldn't hug his Teddy B. bear. He's best friends with Will, Luca and Alma.
Donny is very playful and curious. He loves playing with his big sister, Doc and his toys. He especially loves playing with kids his age. In the episode "Run Down Race Car", Donny is tired from racing Ricardo Racecar last night and has to go inside to take a nap before Luca comes to play. Also in the episode "Ben/Anna Split!", when Donny accidentally rips Ben's hugging patch off because of a thorn from the rosebush he shows Alma and then immediately apologizes to her.
Donny can be easily saddened when he has no one to play with or if his toys are broken, but he can trust Doc to fix up his broken toys. Donny is also always a loving son to his parents. Donny appreciates his big sister, and he knows Doc's always there for him when he needs her.
Donny is a small and slender young African-American boy with curly brown hair, dark skin, a yellow T-shirt with an orange penguin on it, jean trousers and sneakers. In the snow he wears a light and dark orange jacket and a yellow scarf. He has red gloves, a red hat and green boots.
For Halloween in "Hallie Halloween" he wore a clown costume. In "A Very McStuffins Christmas", "Snowy Gablooey", "Night Night, Lala" and "The Doc McStuffins Christmas Special" he wore pajamas with a red top and green pants. His pajama top had reindeers on it.
- "You gotta save him. He's got a hole and he's losing air!"
- "Ladies and gentlemen, you are about to watch the world famous Ricardo Racecar win another race."
- "Doc, thanks for playing with me. You're the best sister ever."
- "Doc, you're the greatest!"
- "I'm gonna play all the games in the whole arcade!"
- "Dad, look! I'm shining the flashlight on Mars!"
- "Come on! Let's go on the slide. Doc will tell us when she's done. Race you there!"
- "Sorry, Doc. Are you OK? I didn't mean to hurt you."
- "Luca! Wow! You brought your rescue helicopter? That thing is awesome."
- "Donny to the rescue!"
- "Hey, cool. Walkie-talkies and spy goggles? We can spy on anyone!"
- "Don't worry. Awesome Guy will save her.
- "Doc, do you wanna have a water fight? Huh? Do you wanna?"
- "Doc! Meet you at the water park!"
- "Teddy B.! Wow, I missed you so much, Teddy."
- "Teddy, I missed you. And I'm never gonna let you go again. Ever. Thanks, Doc."
- "Check out the toy I won at the arcade. His name is Bronty. He's so big, it's awesome. Watch him stomp around. Stomp, stomp, stomp."
- "She's a cowgirl, 'cause she's a cow and a girl"
- "Now that we're adopting a baby, my mom and dad are never gonna have time for me. The baby's gonna take my place."
- "How can a toy pick someone? That doesn't make any sense."
- He plays soccer, just like his older sister.
- It is unknown if "Donny" is his full name, or it could possible be short for "Donald" or "Donavan".
- He is allergic to dust. ("Dusty Bear")
- He is a part of the Turtle Troopers. ("Training Army Al")
- Donny plays the oboe. ("Commander No")
- At one point when he was a baby Donny had gotten his leg stuck in between the bars of his crib. ("Don't Fence Me In")
- He once had laryngitis. ("Hoarse Hallie")
- Like Emmie, Donny takes piano lessons. (“Pop-Up Paulo”)
- Donny does not appear as a main character in Seasons 4 & 5, but he was mentioned in Hoarse Hallie and Visiting hours. in season 4. However, he did returned in two Season 5 episodes called "The Doc McStuffins Christmas Special" and "Lost and Found" to make his final appearances of the entire series.
- Despite being completely absent in season 4, he dose make an cameo in a photo in Welcome to McStuffinsville, CeCe's First Bath, The Lake Monster and Dixie Gets Glued.
- In Donny’s finale two appearance on the show, he dose not wear his usual cloths.
- The Doc McStuffins Christmas Special is Donny’s last speaking appearance, while he doesn’t speak in Lost and Found.
- Donny appears in 84 episodes while he is absent for 52 episodes in the series.
- He, Marcus and Chilly are the only main characters who didn’t appear in the first episode since they made their debut in the second episode. He and Mr. McStuffins are the only two main characters who didn’t appear in It's a Hard Doc Life.
- Donny and his sister Doc are the only main characters who has more then one voice actor.
- Though Stuffy has a different voice actor in The Doc Files.