Cheshire and the Magic Squares

Cheshire doesn't think himself very bright because of dust in his head fluff and stuff. Jay is now 11-years-old so Jay's trying to put away his "baby stuff." Meanwhile, Jay's little sister, Tricia, brings new and somewhat real adventures into Cheshire's life. He wonders how she got here noticing Jay's Mom was fat then suddenly flat. Tricia is the one which gets him out of the house when they go to visit her in the hospital.
Cheshire and the Magic Squares is written first-person through the eyes of Cheshire. Cheshire being bored escapes to a magical kingdom called the Land of the Forgotten where he meets some unusual friends.
At which point, he learns new games and becomes the amazing detective Cheshire Homes but not before he learns what a snickerfit is.
There is a note at the end to parents which explains the inspiration of the story--and also gives a warning.