A man walks into a bar and places a frog and a rat in the counter.
"What's this?" says the barman.
"Just watch," says the man, and places the frog on the bar piano stool. The frog immediately begins to play the accompaniment to a Puccini aria, not very well. The barman is impressed.
"That's nothing," says the man, and gives the rat a nudge. The rat starts singing the aria in a beautiful tenor voice.
"Wow, what an act! You could make your fortune with that," says the barman.
Just then an impresario enters the bar. The barman draws his attention to the remarkable performers, and after some persuasion the man gives another demonstration. The impresario is highly impressed, and offers the man fifty thousand pounds for the act. The man ponders this.
"Well," he replies at last. "I'll take twenty-five thousand for the rat. But I couldn't possibly part with the frog."
After some haggling, the impresario settles for this and leaves with his new acquisition. The barman is perplexed.
"But - why did you sell that beautiful singing rat but insist on holding on to the frog? He's not even a very good pianist."
"No," says the man. "But he's a brilliant ventriloquist."