"Grandpa The Frog" joke

A sister and brother are talking to each other when the little boy gets up and walks over to his Grandpa and says, "Grandpa, please make a frog noise."

The Grandpa says, "No."

The little boy goes on, "Please... please make a frog noise."

The Grandpa says, "No, now go play."

The little boy then says to his sister, "Go tell Grandpa to make a frog noise."

So the little girl goes to her Grandpa and says, "Please make a frog noise."

The Grandpa says, "I just told your brother' no' and I'm telling you' no'."

The little girl says, "Please... please Grandpa make a frog noise."

The Grandpa says, "Why do you want me to make a frog noise?"

The little girl replied, "Because mommy said when you croak we can go to Disney World!"