Books in the Shiny Pippin series

Pippin and her little mouse Tony are playing hide and sleep seek in Granny's garden, when Pippin peeps into the garden shed, and sees a very strange door that she's never noticed before. How did it get there, and where does it lead to?Well one thing it leads to is a crazy new adventure for Pippin, Granny, Mungo, Tony, Oddplop the frog.