That "singing frog" made its appearance in a Warner Brothers' cartoon dating from the late 1940's or early 50's.
A construction worker opens a box in an old building being demolished and finds the frog, which dons a tophat and twirling a cane, begins strutting about in a dance number and singing the same song you mention.
The worker thinks he has made his fortune with this discovery only to find the frog only performs in his presence, elsewhere, the frog is common amphibian, occasionally uttering a long drawn out "crooooooaaaaaak". Frustrated, the worker replaces the frog in a "timebox" and places the box in a building under construction.
At some point in the distant future, another worker demolishing the now obsolete structure discovers the box, and within it, the singing frog.
This is an animated short, not a feature movie.
Is it possible you are combining two or more memories?
Thanks, and that also sounds very familiar to me and I believe I have seen it on tv before, but I've asked another person whom I watched this movie with and he says he remembers it too. It's too clear in my mind to just be an animated short and I remember it being with real people because it was one of the first movies I watched without cartoons in it.
Does anyone else have any ideas what it might be?