Guess Who This Toothy Tot Turned Into!

Before this brown-eyed girl was a well-known actress and activist, she was just another cute kid posing with a mullet in Houston, Texas.

This toothy tot grew up overnight when she became the leading actress in a romantic comedy -- starring alongside her on-screen love interest, Mark Ruffalo. Throughout her long career, she has not only acted in comedies but critically acclaimed films as well ... such as the Oscar-nominated movie "Dallas Buyers Club."

Now a mother of 3 kids, she shares her parenting duties with a famous actor, director and superhero.