In 1971, this ferret played a key role in the construction of particle accelerators at Fermilab's Meson Laboratory. As sections of vacuum chamber were connected together, Felicia would run through them, dragging a string. After she had carried the string all the way through, researchers would use the line to run a rag doused in cleaning solution through the long, narrow tubes.
Particle physics is seldom this adorable, and Felicia became a media star — until her retirement in December of 1971 (scientists replaced her with a vacuum-chamber-cleaning robot). She died the next year of an intestinal abscess. But her memory lives on.
Read about Felicia in the Fermilab archives
Thanks, Jennifer Ouellette!