As Mary examines her green hand in shock, a sound catches her ear. It's a faint hum, but it grows stronger over time. She singles it out, listening very carefully before finally figuring out what it is.
It's a housefly, buzzing around the room. Suddenly, she's reminded that she's fairly hungry, and watches the fly with rapt attention, waiting for the opportune moment. Finally, it lands on the wall, and Mary strikes with blinding speed, her tongue lashing out and stretching across the room in the blink of an eye, catching the fly and pulling it back to her mouth.
She stands there wide-eyed for a few minutes, shocked at what she had just done. Did she just stick her tongue out and eat a fly? She takes a second look at her hand, at her now elongated fingers, with thin, webbed skin between each one, and a sticky, balled fingertips perfect for climbing with. Her feet feel cramped, so she takes off her shoes only to see the same symptoms on her feet as she does on her hands.
She is unable to do anything but stand, slowly enlargening mouth agape in utter shock as she realizes what she took, and what she's becoming - a tree frog.