My Think-a-ma-Jink by Dave Whamond

From chapters.ca:
It's Jack's sixth birthday and he couldn't be more... bored? Model airplanes, stuffed dinosaurs, and talking robots can't even break him out of his bad mood. Enter a mysterious gift from an equally mysterious Uncle Doug. Within an ordinary- looking brown box glows the Think-a-ma-jink, a bizarre contraption that claims to bend the laws of time and space. With this gadget, no idea is too fantastic to be realized, no world too distant to be visited, no personality too zany to be adopted. With his younger sister, Marie, at his side, Jack discovers a wild new universe of possibilities before him. But when he and Marie engage in a boisterous, shape- shifting struggle, the future of the Think-a-ma-jink hangs in the balance. This is a picture book about infinite possibilities - a wonderful story of the power of imagination over even the fiercest rivals - be they yetis and dragons or a little case of the blues.