Honk the Moose, by Phil Strong

Honk the Moose is a true story! In Birora, Minnesota, two friends, Waino and Ivar, are returning home from skiing. Ivar's father owns the livery and the two boys stop in his stable to oil their skis. But amidst the horses, they discover a moose, who wandered in to help himself to the hay after going hungry for days in the harsh winter. He is named Honk for the sound that he makes, and try as they might, Honk cannot be convinced to leave.

The story will be very fun as a read-aloud, especially as the effort to remove Honk escalates in the town, with each new person not believing that the moose really exists (first Ivar's father, who sends the boys to call the police, who calls the mayor, who then calls the town council). When it becomes clear that Honk is there to stay, the book talks about how he becomes a part of the town. This one's more for younger readers of chapter books, but still a fun story for older ones.