At some point prior to the start of the series, Grenda became best friends with Candy Chiu, as seen in the episode "Double Dipper." Her voice was not always deep, as mentioned in "Double Dipper." At some point, her voice changed.
In "Double Dipper," Grenda and Candy go to the party that Stan Pines hosts at the Mystery Shack together, also bringing what seems to be Grenda's pet iguana or an iguana that she is taking care of, and it is there that they meet Mabel. Grenda is the first to talk to her, and introduces her to Candy as well. She and Candy cheer for Mabel while she tries to win the party crown in a competition against Pacifica Northwest.
Grenda tells Mabel that she wants to put Pacifica in a headlock and "make her feel pain" after Pacifica insults Grenda's voice by saying that she sounds like a wrestler. After Pacifica wins the crown and leaves with most of the party goers, Grenda and Candy announce their intent to have a sleepover with Mabel, and how happy they are that they are now friends. Then the three girls start dancing, Presumably, they spend the night at the Mystery Shack.
Grenda appears again in "Summerween," dressed as a witch, and goes trick-or-treating with Candy, Soos, Dipper, and Mabel. Stan asks her if she has a cold due to her voice, which upsets her. She is one of the witnesses of the Summerween Trickster's appearance, and helps Dipper and Mabel collect five hundred pieces of candy to satiate the creature. Later, when they're fighting with the monster, she tastes him and exclaims, "Saltwater taffy? Gross!"
In "Carpet Diem," Grenda and Candy go to Mabel's house to have a sleepover, where they are shown playing "Calling All Boys: Preteen Edition," and talking to a robotic-voiced boy named Kevin. Later, they find Dipper in Mabel's body and take him upstairs for a second sleepover. After Dipper and Mabel switch back, Mabel tells the girls about the electric carpet's magical properties.After tring to stop the twins from fighting Grenda switches bodies with several other people, including Old Man McGucket, Waddles, and Mabel. In the end, everyone ends up back in their own bodies.
In "Boyz Crazy," Grenda, Mabel, and Candy attempt to attend a Sev'ral Timez concert, only to find that it was sold out. Afterwards, they sneak backstage, discovering that the boy band members are actually clones being held as slaves by their producer. They release the boys and bring them to the Mystery Shack. Soon after, Mabel becomes highly possessive of them, forcing Grenda and Candy away. Eventually, Mabel decides to let the band go, and the three release them into the wild.
In "Gideon Rises," she and Candy reappear as Dipper and Mabel prepare to leave Gravity Falls. The two girls are seen comforting each other. They do not appear after that, not even when the rest of the town gathers around the remains of the Gideon-bot at the end of the episode.
In the short "Mabel's Guide to Fashion," she commentates on Mabel's fashion show, and helps her in Soos' "flash makeover." She also comments favorably on Mabel drawing a face on Old Man McGucket's bald spot.
In the short "Mabel's Guide to Color," Mabel asks her what her favorite color is, and she replies "Biege!" Later, when Mabel calls for ideas on how to get Stan to see a rainbow, Grenda says that she sometimes sees rainbows when she drinks expired milk, and proceeds to do so while Candy draws up a plan to reflect a rainbow from a waterfall. Upon finishing the milk, she speaks up in agreement to Candy's plan before collapsing to the floor and falling asleep.
Grenda briefly appears in the "Little Gift Shop of Horrors" segment Abaconings. She tries out a jet pack built by the newly-superintelligent Waddles.
In "Northwest Mansion Mystery," Grenda attends the Northwest Fest with Candy and Mabel. The three friends are excited about the prospect of meeting cute rich boys at the party, and when they arrive, they find out about Marius von Fundshauser, a 13 year old baron from Austria. Grenda, Candy, and Mabel make a truce not to flirt with Marius because he is "out of their league," but Mabel and Candy flirt with him behind Grenda's back, rationalizing that Grenda's flirting technique is too aggressive. Grenda finds out about this and deliberately flirts with Marius in an aggressive way to get back at Mabel and Candy. Later, Grenda, Candy, and Mabel are turned to wood by the Ghost of Northwest Manor. Once they are restored to normal, they make up, after which Marius approaches Grenda and says he can't stop thinking about her and gives her his phone number.
In "Dungeons, Dungeons, and More Dungeons," she plans to watch the Duck-tective season finale with Mabel and Stan, only to find that Dipper and Ford have taken over the living room with their game. Terrified, she stomps on their graph paper. After Probabilitor the Annoying kidnaps Dipper and Ford in order to eat their brains, Grenda joins Mabel and Stan on the rescue mission, bringing along a chair as a weapon. Later on, she uses the chair on an ogre, seemingly killing him. When Probabilitor is defeated, Grenda hugs the Hot Elf as he and his master fade back into their dimension. Afterwards, she, Stan, and Mabel watch the Duck-tective finale. Grenda is angered by the reveal that Duck-tective was shot by his twin brother, calling it a rip-off.
Mabel calls her, Candy, and Wendy in "The Last Mabelcorn" to accompany her on a magical quest to find a unicorn and acquire some of its hair to protect the Mystery Shack from Bill. Grenda uses her deep voice to their advantage, bellowing an ancient druid chant written in Journal 1 to summon a unicorn. After Celestabellebethabelle makes Mabel doubt her morality, she and Candy follow along with Wendy's plan to take the unicorn's hair by force. The plan involves Grenda trading illegally trafficked butterflies with a gnome for fairy dust to knock Celestabellebethabelle out with and then turning the gnome over to the police with a bribe of half the dust she was given. When Mabel catches the other girls about to cut off some of the unconscious unicorn's hair and inadvertently wakes her up, two other unicorns show up to expose her "pure of heart" test as a sham. This leads to an all-out brawl between the girls and the unicorns that ends with all four covered in rainbow-colored fuids. They leave the enchanted glade with the desired unicorn hair and a large treasure the unicorns gave them to get rid of them. Grenda also left wearing a set of unicorn eyelashes.
In "Roadside Attraction," Grenda joins the Pines, Soos and Candy on their RV trip to prank various tourist traps around Oregon. On their travel, the children assist Stan on various pranks on the other tourist traps. During their stop before traveling to Mystery Mountain, Mabel, Candy and Grenda play "Truth or Dare or Don't," Candy tells the girls her crush on Dipper, Mabel and Grenda helps Candy get closer to Dipper during their trip. When Candy returns after being heartbroken during her date with Dipper, Grenda and Mabel comfort her. Dipper comes and asks the girls for their assistance on helping Stan who got caught by Darlene. The kids run to the mountain and save Stan and as they escape, they ride a slow moving tram which Darlene encases with web when she catches up. Candy releases the tram which sets of a chain of events which eventually leads to Darlene's fate. As they travel back, Grenda joins the others in front of the RV as they travel back to Gravity Falls. She, along with the Pines and Candy, see the Mystery Shack vandalized by the owners of the tourist traps they pranked.
In "Dipper and Mabel vs. the Future," Grenda tells Mabel that she's going with Marius to Austria to hang out as his "castle or whatever." Mabel is disappointed that she won't be around to come to her and Dipper's 13th birthday.
In "Weirdmageddon 2: Escape From Reality," Grenda and Candy are revealed to have avoided capture or madness and have joined Stan's Resistance Group, who reside in the Mystery Shack.
Grenda appears for the last time in "Weirdmageddon 3: Take Back The Falls," saying goodbye to Dipper and Mabel as they leave Gravity Falls.
PersonalityGrenda is insecure about her low, gruff voice, and is constantly belittled, as well as made to feel weird and out of place by popular girls such as Pacifica Northwest. This tends to make her uncomfortable, sad, and angry. She seems very supportive of her friends and while with them is usually happy. She, like the rest of her friends, likes to talk about boys.
Grenda is a light-skinned, large girl with auburn colored hair and a ponytail. Grenda wears a pink shirt that reads "COOL", and purple shorts as well as white socks and pink and purple sneakers. She also has a red mark on the right side of her cheek, and a yellow barrette on the hair on the right side of her head. In "Carpet Diem," she was shown in her sleepwear; a long pink nightdress with a purple bear head on it. Underneath the bear head, "BEAR" is written in purple, similar to her shirt. In "Northwest Mansion Mystery," she wears a homemade gold dress (and matching scrunchie) with aqua pearl earrings, a matching necklace, a single shoulder strap with blue corsage, and blue strap shoes to Northwest Fest.
- At the 2013 San Diego Comic-Con Gravity Falls panel, Alex Hirsch stated that Candy and Grenda are Mabel's "life-long friends."
- Her favorite color is beige.
- She will apparently marry rich.
- Grenda is strong enough to lift a recliner with relative ease and durable enough to smash a large rock on her face with no sign of pain.
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