Gretchen (voiced by Ariel Winter) is one of the Fireside Girls in Danville Troop 46231.
She was one of the Ferbettes in Phineas and the Ferb-Tones ("Flop Starz", "Phineas and Ferb Musical Cliptastic Countdown"). She also helped Phineas Flynn win the Swamp Oil 500. Isabella Garcia-Shapiro thanked her for a job well done and complimented her on adding the bow to the Team Phineas Race car during the pit-stop ("The Fast and the Phineas"). She also sings in S'Winter ("S'Winter"). In a deep voice, she counts down the blastoff of Phineas and Ferb's rocket when they visit their star ("Out to Launch"). She appears to have a large IQ, having to repeat her statements due to the others not understanding what she had said, and saying words that no one else in the room knows (""Bubble Boys", "Isabella and the Temple of Sap").
Gretchen has rather short auburn hair, blue eyes with glasses, and wears her uniform with a large collar, bell-shaped sleeves, a red belt around her skirt, and low-top shoes, and is slender.
In winter, however, she ties her hair into a mid-length ponytail with a red elastic, and wears an orange and red long-sleeved shirt with brown pants, and orange slip-on shoes.
- Help Thy Neighbor Patch (About 52 as of "Isabella and the Temple of Sap")
- Aquatic Safety Patch
- Sewing Patch
- Tent Pitching Patch, Marshmallow Patch
- Aeronautic Patch
- Broadcasting Patch
- Shrimp Net Repair Patch
- Saying A Word No One Else In The Room Knows Patch ("Sesquipedalian"), Sap Collecting Patch
- Mountain Moving Patch
- Rodeo Clown Patch
- Desert Tracking Patch, Rain-forest/Jungle Navigation Patch, Rock-climbing Patch, Non-power Flight Patch, Concussion First-aid Patch
- Flier Delivery Patch (Twice "The Remains of the Platypus")
- Gretchen is voiced by Ariel Winter. She is the first of the Fireside Girls after Isabella to have a speaking role in the series.
- She and Katie are the only Fireside Girls who appeared in the Phineas and Ferb Nintendo DS game.
- In "Isabella and the Temple of Sap," she appeared to take the most prominent role, having the most spoken lines of dialogue.
- She may be a reference of Velma from Scooby-Doo, whom she resembles in several ways, and may be the girl using the catchphrase "Jinkies" off-screen in that episode.
- She shares a few traits with an earlier character from Disney with the same name, Gretchen Grundler from Recess. Both girls have red hair and glasses, and both are very kind and smart.
- She is the only Fireside girl along with Katie and Milly, to appear in "Disney's Phineas and Ferb: The Best LIVE Tour Ever!"
- She was the only Fireside Girl who didn't appear in "Phineas and Ferb Christmas Vacation!", but appeared for a cameo in "A Phineas and Ferb Family Christmas".
- She is the only Fireside Girl (besides Isabella) to have a part of the "Too Young" line ("Isabella and the Temple of Sap") and the only female (besides Candace) to have the "Out, peace!" line ("Monster from the Id").
- In The Ballad of Badbeard, she appears to get seasick.
- Gretchen appears to be the shortest of the main Fireside Girls (All episodes that all the Fireside Girls are in) and the lightest as Adyson Sweetwater were able to carry her weight while she was reading "The Fireside Girls Book of Dendrology" (a large, heavy book) with no problems in "Isabella and the Temple of Sap."
- At first glance, it may be difficult to tell which of the Fireside Girls is Gretchen. Early on in the episode, she is the girl who asks the question about Phineas' racecar being electronically fuel injected; however, she is not given a name at this point. Her name comes later when Isabella compliments her on the bow she ties on the car, but it is unknown which Fireside Girl she is since Isabella was speaking to the group. The last piece to the puzzle is that Ariel Winter is credited as Gretchen in the end credits for the episode "Out to Launch". However, Katie has also spoken in the episode. Therefore, she has a speaking part in the episode, and must be the Fireside Girl who asks the question. The episode's print novelization in Speed Demons further confirms this by way of the narration explicitly stating that it is Gretchen who asks the question.
- "Lawn Gnome Beach Party of Terror" (Cameo)
- "Flop Starz"
- "Candace Loses Her Head" (Cameo)
- "The Fast and the Phineas" (first speaking role)
- "Raging Bully" (Cameo)
- "Lights, Candace, Action!"
- "Jerk De Soleil"
- "Mom's Birthday"
- "Get That Bigfoot Outa My Face!" (Cameo)
- "The Ballad of Badbeard" (Speaking cameo)
- "One Good Scare Ought to Do It!"
- "The Flying Fishmonger"
- "Put That Putter Away" (Cameo)
- "Tree to Get Ready"
- "It's About Time!"
- "Out to Launch"
- "Tip of the Day"
- "Day of the Living Gelatin"
- "Don't Even Blink"
- "Chez Platypus"
- "Thaddeus and Thor" (Cameo)
- "De Plane! De Plane!"
- "Let's Take a Quiz" (Cameo)
- "At the Car Wash"
- "Oh, There You Are, Perry"
- "That Sinking Feeling"
- "Spa Day"
- "Phineas and Ferb Musical Cliptastic Countdown"
- "Bubble Boys"
- "Isabella and the Temple of Sap"
- "Fireside Girl Jamboree"
- "Candace's Big Day"
- "I Was a Middle Aged Robot"
- "Robot Rodeo" (Cameo)
- "The Lemonade Stand"
- "Phineas and Ferb Summer Belongs to You!"
- "Wizard of Odd"
- "Rollercoaster: The Musical!"
- "The Great Indoors"
- "Phineas' Birthday Clip-O-Rama!"
- "Ask a Foolish Question" (Mentioned)
- "Tour de Ferb"
- "A Phineas and Ferb Family Christmas" (Cameo)
- "Monster from the Id"
- "The Remains of the Platypus"
- "What A Croc!"
- "Ferb TV"
- "The Last Day of Summer"