Christopher Robin is a character in a children's story. There was a real Christopher Robin, who, as a child, admired a bear at the zoo in London. The bear was brought to England by Canadian troops in 1914, and as their regiment came from Winnipeg, in the Canadian province of Manitoba, the bear was named Winnie. So Christopher Robin's father wrote a series of stories about a child's stuffed bear named Winnie the Pooh, and in the stories, Christopher Robin and Winnie the Pooh have adventures together.
This is an illustration from the original books of Christopher Robin reading to Winnie the Pooh.
Expotition is a case of the author mimicking the errors that children sometimes make with large words that they don't really understand. The word which is wanted in this case if
expedition, which is a group of people who set out to accomplish a goal, often a difficult one.