Susannah L. Test
Susan (2).png
Powers and abilities Intelligence


Gender Female
Age 13 (Season 1)

14 (Season 2-7)

Hair Color Red
Eye Color Blue
Status Alive
Aliases Test Sister, Girls that I've never seen before, Sarah (by Gil)
Personality Intelligent

Loving (for some reasons)
Caring (for some reasons)
Kind (for some reasons)

Friends Gil Nexdor (for some reasons)
Mr. Black
Mr. White
Johnny Test
Mary Test
Enemies Bling-Bling Boy
Dark Vegan
Zizrar the Mole King
Mr. Mittens
Brain Freezer
The Tickler
Jillian Vegan
Evil Johnny
Alignment Good
Love Interest Gil Nexdor (true crush)
Bling-Bling Boy (one sided, on his side)
Sutton and Gary
Likes Gil Nexdor, inventing, science, video games, skateboarding, fighting, rock music
Dislikes Bling-Bling Boy and his obsessive behavior, Johnny misusing her inventions, Johnny's annoying, selfish, and rude behaviour (at times)
Family Lila Test (Mother)
Hugh Test (Dad)
Mary Test (Older twin sister)
Johnny Test (Younger brother)
Pets Dukey (Dog)
First Appearance Pilot Episode
Voiced by Maryke Hendrikse

Laurie Hymes (Web Series)

“I can't believe it. You can't be my twin sister.”
— Susan arguing with Mary at "Johnny to the Center of the Earth".

Susannah Laura "Susan" Test is the twin sister of Mary Test and is the youngest of the two twins. She is one of the tritagonists of the series and by 1-2 years older, the older sister of titular character Johnny Test.


Susan is a super genius scientist. She is the twin sister of Mary, (being around almost 14) as she is boyish and tough as her brother Johnny, but like her sister, Susan cherishes a deep love and obsession for Gil.

Bling-Bling Boy (A.K.A. Eugene) has a huge crush on Susan but whenever he gets her to fall in love with him it always fails, mainly because Johnny foils him or Susan turns him down (Susan often rejects Bling Bling Boy's advances, as she finds him repulsive). Like her sister, she attends school at the Porkbelly Institute of Technology. Susan is prone to believing in the more scientific and logical explanations for things rather than the illogical and magical explanations. Her sister is more open-minded, and Mary is frequently proven correct. Susan seems to be less level-headed than her twin Mary, and tends to be less conservative, as she speaks her mind much more frequently.



She is head over heels for Gil. She does things with Mary from watching him from satellite in their lab and trying to hang out with him. Also, despite the fact that Gil has been living next door to the girls for most of his life, he often forgets them, much to their dismay.


Susan is Johnny's sister and generally assists Johnny and Dukey with their creative inventions. For some reasons, she gets annoyed by Johnny and is more likely to explode at him whenever his antics get under her nerves, but she still loves Johnny as a brother.


Susan loves her father, but despises his meat loaf and his constant punishments for doing experiments and studying them on Johnny.


Both have a good mother-daughter bonding.


For some reasons, Dukey truly annoys Susan, but he still has respect for her as she's one of his owners.

Bling Bling Boy

Bling Bling Boy has a crush on Susan for a long time. However, she does not share the same feelings of love.

Within one or two episodes,Susan and Bling-Bling Boy had shared a kiss, Although Susan claims it was a robot who kissed him instead of the real Susan Test.

Appearance and Design

Susan has fully very long straight red hair and blue eyes. She wears square glasses. Without her glasses, she has very poor vision and her eyes show strain. In Downhill Johnny, her eyes are big blue dots, whereas in later episodes, she has normal eyes (albeit somewhat smaller than those of other characters). She wears a pastel blue shirt with a blue star on it, a black skirt and socks with black Mary Jane shoes. She is always seen wearing a lab coat. She wears a star-shaped hairclip. She wears a blue one-piece bathing suit; this is usually when sunbathing or at the beach. She also has suits for certain controlled experiments, such as a hi-tech diving suit, and a tight-fitting yellow hazmat suit. Both suits have her trademark star on the side. For some reasons, she wears a pair of blue latex gloves, and a surgical mask when handling bio hazardous materials, namely during surgeries. In Magic Johnny, she wears a pastel blue shirt with a blue star on the breast, a blue beret, and her skirt. In her music video outfit, she wears a blue top that reveals her midriff, a blue hat, a black skirt with a pink belt around it, blue over-the-knee socks, and pink flats. Her pajamas are deep-sky blue with white shining stars. As a vampire, Susan dons a long, black dress that covers her legs, with her dress having alot of purple accents on it, including a large cape that acts like wings whenever she flies, just like Mary's dress, and a small red spider can be seen at the front of her dress. Her star also becomes purple, and her eyes becomes chartreuse, with 2 long and sharp fangs sticking out of her mouth, just like Mary.


  1. Su. Her counterpart in Leadbelly is named Simon West.
    • The colors on Simon's shirt switch places with the colors on Susan's shirt.
  2. Susan and Mary's catchphrase is "We're such geniuses".
  3. She and Mary are extremely ticklish, as was revealed in the episode "Johnny vs. The Tickler" She and
  4. She and Mary are revealed to suffer from plantar hyperhidrosis, "stinky feet", in "Johnny Unplugged".
  5. Susan has a bigger temper than Mary, similar to her mother's. Quantum of Johnny and Future Johnny are the only episodes she doesn't appear in.


Susan test.png


"You cannot be my prodigy genius twin sister!" "Now hold still, this won't hurt a bit, it's gonna hurt a lot."

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