This was posted on the groaners listserv. It is by Himie Koshevoy.

To celebrate Canada’s Centennial year of 1967, Vancouver, British Columbia, built a magnificent planetarium that has played to standing room audiences since it opened. Many of its visitors are students of secondary schools, and one school decided to produce a play wherein the student players would enact the roles of heavenly bodies. The teacher who had written the play, chose her cast and awarded the roles to those who would play the Sun and the planets in the galaxies.

Shirley, devoted to astronomy, was given the part of a minor planet, but she wanted only the key part of the Dog Star, one of the sky’s brightest stars. Shirley tried everything. She importuned. She was tearful. She ranted, and when she finally began a campaign of remarks disparaging to the girl who did get the part.

The exasperated teacher finally stopped all her arguments, shouting, “Shirley, you can’t be Sirius!”