Experiment 255 was the 255th genetic experiment created by Jumba with Hämsterviel's funding. She was designed to make anyone sick with her obnoxious fumes. 255 and the other first 624 experiments were deactivated and smuggled to Earth by Jumba during his mission to capture Experiment 626.
All of the experiment pods were released and scattered across the island of Kauai.
Mrs. Sickly is a light teal Mr. Stenchy-like experiment with golden eyes, puffier antennae and smaller hair.
Powers and abilities
Like Mr. Stenchy, Mrs. Sickly appears disarmingly cute to everyone else except other experiments and emits an extremely foul and noxious odor 48 hours after she is activated. Additionally, if Mrs. Sickly's emissions intermix with Mr. Stenchy's sour emissions, the chemical reaction will cause a cataclysmic explosion capable of destroying the planetary body they inhabit.
Mrs. Sickly first appeared when she was released by Hämsterviel along with Mr. Stenchy during Christmas in Japan. This is when it is revealed that if the emissions from these two mix, they have the power to destroy entire planets. This leads to Yuna, Pleakley, Stitch, Jumba, Hämsterviel, and Gantu on a hunt to round up the clones of Mrs. Sickly and Mr. Stenchy in order to save the world's Christmas, as Hämsterviel mass produced the clones and sold them to many children across Japan and the rest of the world.
- Mrs. Sickly is one of the rare experiments to have sclerae and pupils instead of solid black eyes, the others being Mr. Stenchy, Skip, Clink, Nosox, and Bragg.