Listed in the credits of the film The Toxic Avenger (1984), actress Marisa Tomei supposedly was an extra in the film:
Little credit can be given to IMDb (when IMDb was in its infancy, anyone could edit anything on it based on a hunch), and she is indeed "uncredited" in the film.
When looking for a screenshot of her scene on search engines, an extra with very different physical features shows up in search results.
Several internet users have pointed out that the extra doesn't look anything like Marisa Tomei.
Additionally, according to the slide show located in the Special Features section of the Director's Cut DVD released in 1981 by Troma, Marisa Tomei briefly appears as an extra in the scene where Melvin runs away from the pool before jumping out of the window and falling into the toxic waste (hence not this scene).
However, IMDb lists producer Dolly Hall as "Girl in Health Club", who looks a lot more like the extra in question (hair color, hair part, eyelashes, eyebrows, facial shape, nose shape and eye color are a much better match).
There are also plenty of background extras with black hair that would more likely be her.
So there are a few possibilities:
Marisa Tomei was never in The Toxic Avenger, someone edited this entry mistakenly in IMDb many years ago and no one cared to fix it, the false information was then subsequently reshared overwhelmingly;
She was in a scene of the film, and the person who added this information is correct but her scene didn't make it to the final cut;
She is in the film, but the credit is wrong and she is in another scene where her face is not clearly visible, and viewers who share this screenshot saying it is her are mistaken;
This is Marisa Tomei and somehow her hair color, hair part, eyelashes, eyebrows, facial shape, nose shape and eye color looked different on that occasion.
This extra's name is Marisa Tomei, but not the Academy-Award winning actress Marisa Tomei.