She was voiced by Candi Milo.
Sweetie is a young, pink female canary, who wears a light blue bowed ribbon in her hair. She attends Acme Looniversity and lives in Acme Acres. Her mentor and favorite teacher is Tweety. Sweetie's pink coloring, devious grin, and somewhat mean-spirited personality seem to be a throwback to Tweety's early appearances.
Sweetie is voiced similarly to comedian Judy Tenuta—speaking in a liquid trill followed by a throaty screech (when excited). Her voice rises to a deeper, more sadistic tone when she is about to harm, eat, or squash something or someone. Her voice can quickly go from sweet to tough as nails.
Sweetie uses a delicate flutter when she flies and toddles on the ground in a cute "baby" walk.
Sweetie's diet consists mainly of worms, horse-flies and other insects. She usually refers to a bug as "a tiny, little morsel," or "a tasty, tender McBugget." Sweetie has a ravenous appetite for worms, but the elusive Bookworm is much too smart to fall for her "sweet" facade. Often the tables get turned on Sweetie and she is pursued by Furrball, who she inevitably ends up clobbering mercilessly. Depending on the cartoon, Sweetie lives in a treetop nest, in a birdhouse, or in a cage at Elmyra's house. In most of these cartoons, Furrball is chasing the little bird, who always manages to annihilate him.
Abandoned as egg, Sweetie grew up tough on inside and tender on outside. Sweetie's personality tends towards behaving in amiable manner, but is prone to a mischievous streak dealing with her main enemy, and long-time pursuer, Furrball. Completely sweet, yet totally diabolical, our sleepy-eyed baby hatchling is somewhat of a Dr Jekyll/Mr Hyde.
- She sadistically torments Furrball for no reason.
- In "The Looney Beginning", she squashed Furrball with a mallet for no reason.
- In the episode "Squish", within a nightmare Dizzy Devil has, Sweetie attempts to eat a bug-sized Dizzy when he, stuck with gum and then shot by Furrball, has flown into a branch above Sweetie's nest. When he falls, she tries to step on him, claiming it "won't hurt a bit!"
- In "Let's Do Lunch", she was trying to get Furrball to eat her, because she wants Elmyra to kick Furrball out of the house.
- In "Eating Between The Lines", she tried to eat Bookworm.
- In "Cross-Country Kitty", Sweetie takes advantage of Furrball twice (okay, three times because one way was repeated): when Furrball arrives and attempts to eat her behind Mary Melody's back, he ends up eating her horsefly; however, when she reveals it to him and he spits it out, she force-feeds him more straight from the box. The next time, she pretends to hold a surprise birthday party for him and has invited "all [his] friends": vicious dogs that scare him off. Once he and Mary Melody have returned from their vacation, she "welcomes" him home with the dogs, scaring him off back into the alley.
- In another episode, Sweetie programs Furrball not to eat birds, but rather to eat Arnold instead.
- In the episode "Debutante Devil", when Dizzy Devil lands in a boxing ring, she counts slowly to two, but rapidly counts the rest of the way to ten, and bangs something clanky on his head.
- She is very similar to Jerry Mouse from Tom & Jerry as both are sadistic and torment their predators (Sweetie to Furrball and Jerry to Tom), and they receive no punishment for their cruelty.