Tips on entertaining a two year old?

I am babysitting a two year old girl tomorrow, for eight hours while her mom is at work. The longest I've had Addison before is about three hours. She has a fairly short attention span, and gets bored quickly. What can I do to keep her entertained for eight hours? She loves My Little Pony's, Littlest Pet Shop, etc. and adores being outside if that helps at all. Thanks!