Johnny Test Wiki
Susan Test
Susan (2).png
Powers and abilities Intelligence


Gender Female
Age 13 (Season 1-6)

14 (Season 7-)

Hair Color Red
Eye Color Blue
Status Alive
Aliases Test Sister

Girls that I've never seen before (by Gil)
Sarah (by Gil)

Personality Intelligent


Friends Gil Nexdor

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 in "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 two tritagonists of the series and the older sister of the titular character Johnny Test.


Susan is a super genius scientist and the younger twin sister of Mary (both being around 13 or 14) as she is tomboyish and firm 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, 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 often.



She (like her sister Mary) is head over heels for Gil. She does things with Mary from watching him from a satellite in their lab and trying to hang out with him. Despite living next door to the girls for most of his life, Gil often forgets them, much to their dismay.


Susan is Johnny's sister and generally assists Johnny and Dukey with their creative inventions. For some reason, 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 meatloaf and his constant punishments for doing experiments and studying them on Johnny.


Lila and Susan seem to 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.

However, in two episodes, Bling-Bling Boy shared a kiss with Susan, although the first was with a robot look-alike.

Appearance and Design

Susan has very long straight red hair, blue eyes, and wears square glasses. She wears a pastel blue shirt with a blue star on it, a black skirt and white socks with black Mary Jane shoes and a lab coat. She wears a star-shaped hair clip.


  • Susan's counterpart in Leadbelly is named Simon West, although the colors on Simon's shirt are reversed.
  • Susan and Mary's catchphrase is "We're such geniuses."
  • She and Mary are extremely ticklish, as was revealed in the episode "Johnny vs. The Tickler".
  • She and Mary are revealed to suffer from plantar hyperhidrosis, "stinky feet", in "Johnny Unplugged".
  • 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's name is inspired by the word star as star starts with the letter s, she wears a star-shaped hairclip and a shirt with a star on it.
  • While never outright stated, since both Susan and Mary wish to marry Gil, it implies both are aware of the concept of polygamy (a multi-person relationship) and are fine with being co-wives. Considering their genius, it's not like they would be ignorant of something like this.


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."