A young married couple maintains a strict sexual schedule. Every day, the husband and wife get home from work at 5 p.m. and have sex at 5:15 p.m.
One day, the wife comes down with the flu and goes on antibiotics. The medicine kills all the germs, except for three, who huddle together inside her body to talk over survival tactics.
One germ decides to hide from the antibiotics between two toes on her left foot. The second germ decides to hide behind her right ear.
The last germ says, "You guys do what you want, but when the 5:15 pulls out tonight, I'm gonna be on it."