In "The Magic Fish", Coach Tiffany Gills reminisced about her teenage years, in the year 1997, saying she was an early bloomer, and looking fantastic in appearance. Despite her stellar exterior beauty, however, the male fish found her repulsive, because of her deep, gruff, masculine voice, which she's apparently had her whole life. Not only was this with potential boyfriends, but with all friends in general. Tiffany lived a sad and lonely life, before she ended up with the job she holds now.
In "Have Yourself a Joyful Little Animas", it was implied she developed an extreme hatred for Animas (the animal equivalent of Christmas), when she was 7 and still living with her mother. However, the story about this was told through a play, being put on by her co-workers and it's legitamacy is questionable, since Tiffany found a flaw in the act, where her mother, allergic to processed meat, asked for a balonga sandwich.
Coach Gills is a tiny, orange goldfish, who floats in the middle of a larger glass fishbowl of water. Gills has a tall, yellow fin on her head, resembling a lock of curly hair, upon which she wears a blue bow. She has three eyelashes on each of her big, bulging eyes, that often stare off in different directions. She also has a very large mouth, rimmed with pink lips. She has two yellow fins on the sides of her body, serving as her arms and a tail on the back. Often times, she wears a whistle around her neck, that's bigger than she is, causing it to lie down in the floor of the bowl, while her body only supports the back end of the string.
Although Coach Gills looks rather sweet, she's no pushover. She never hesitates to give Adam a hard time if he doesn't perform as well as his fellow students and she does the same of mistreatment to Horace, despite everything he does for her.
Coach Gills is very dependent on Horace, not being able to move anywhere without him. Horace serves her hand and foot and she barks out orders in return. In "The Magic Fish", she said that she had no friends, much to the disappointment of Horace. Coach Gills ignored him, saying their relationship is strictly professional.
Coach Gills is the one who paired up Adam with Jake. She has always been the hardest on Adam, because he is the weakest. In "Le Switcheroo", she and Adam trade roles for a day. After experiencing some trouble with Bull Sharkowski at least, they at last reconciled. But, she had never been surprised that Adam inherited her aggressive voice to get back at Bull and Pixiefrog's antagonistic behavior. Which would be his vocalized defense mechanism.
- Inoculaton Day
- Lyon of Scrimmage
- Bad News Bear
- Chew on This
- The "A" Word
- Amazon Kevin (Cameo)
- Guano in 60 Seconds
- Bubble or Nothing (Cameo)
- Up All Night
- Le Switcheroo
- I Got a New Aptitude (Cameo)
- Disregarding Henry
- Poop Scoop
- The Magic Fish
- Lupe in Love (Non-Speaking Cameo)
- Have Yourself a Joyful Little Animas
- Carny Crazy (Cameo)
- Making the Grade
- Talking Teddy
- The Big Field Trip Part 1
- The Big Field Trip Part 2
- Lie, Cheetah, Steal
- An Inconvenient Goof (Cameo)
- My Feral Lyon
- Robo Frog 3000
- Glazed and Confused
- Synch or Swim
- Animal School Musical
- A Thanksgiving Carol (Flashback)
- A Whole Zoo World
- Her deep, manly voice often gets her mistaken for a male, by other characters and outside viewers alike. The only overarching things that prove her feminine gender would be her eyelashes and her tiny blue bow on her top fin.
- She has mentioned several times, she has no friends. (The "A" Word, "The Magic Fish)
- If her story of being a teenager in the year 1997 is accurate, assuming the series takes place in 2005 (the show's airdate), that would put Coach Gills' current age in her early 20's.
- She once had a crush on Mr. Cheetah, an athletic individual who plans to succeed her and Principal Pixiefrog in their careers. In "Poop Scoop", she was very interested in Adam's 'crush' on her, hinting attraction for him.
- Although she is a fish, she apparently cannot swim. (An Inconvenient Goof)