A mid-1950s construction worker involved in the demolition of the J. C. Wilber Building finds a box inside a cornerstone. He opens it to reveal a singing, dancing frog, complete with top hat and cane. The box also contains a commemorative document dated April 16, 1892. With riches in mind, the man tries exploiting the frog's talents for money. However, the frog refuses to perform for any individual other than its owner, instead devolving into croaking in the presence of others. The man frantically tries to demonstrate the frog's abilities to the outside world, first by trying to get an agent to accept him, then by renting out a theater for it to perform in, to no avail.
After these failed attempts to profit from the frog, the man becomes destitute and is living on a park bench, where the frog still performs only for him. A policeman overhears this and approaches the man for disturbing the peace, but after the man points out the frog as having done the singing, he takes the man in. He is committed to a psychiatric hospital along with the frog, who continues serenading the hapless patient. Following his release, the haggard, broken man spies the construction site where he originally found the frog and joyfully hides the box (with the singing frog again enclosed) in the cornerstone of the future "Tregoweth Brown Building". He then tiptoes away to freedom. The timeline then jumps to 2056 (100 years and at least one day after the cartoon's debut). The Brown Building is being demolished using futuristic ray guns, and the box with the frog is discovered yet again by a 21st-century demolition man, who, after envisioning riches as well, absconds with the frog to start the process once again.