Michigan J. Frog is a cartoon character inspired by an urban legend, and was previously the mascot for the WB television network.

Newspaper accounts indicate that in 1955, a New York City construction worker claimed to have found a frog alive in the cornerstone of a building slated for demolition. Not only was the frog still alive, following an unknown period being sealed in concrete, but the unidentified worker claimed that it could actually sing popular songs of the 1930s in a magnificent baritone. Wagering his own life savings, the construction worker booked a Broadway theater and sold tickets to see his spectacular singing frog; but when the curtain rose, the audience saw only an ordinary amphibian, dressed in the world's smallest top hat and tails. The construction worker was ruined, and never heard from again.

At last report, the actual frog was once more entombed in the cornerstone of what would become the headquarters for the CW network. He is scheduled to be unearthed again in 2055, pending the development of laser demolition equipment and flying cars. Quantum physicists are practically salivating in anticipation.

As a mascot for the WB, Michigan J. Frog was an unusually prescient choice: He presaged financial ruin for his backers, and proved to be lively and entertaining only when no one was watching. He also worked briefly for the Bush administration and received the Congressional Medal of Honor.

The "J" stands for "Jehosaphat Q. Mummfley," a comic strip character from the 1930s.