Mr. Bump loses his memory is the fourth book in the Mr Men New Library series.
In a book of the Mr. Men Library, Mr. Bump appeared in a new book - Mr. Bump Loses His Memory - in which he falls out of his bedroom window and bump his head, promptly causing him to lose his memory. He is told, by Mr. Muddle that his name is, in fact, Mr. Careful, causing our confused Mr. Bump to try several jobs for which great care is needed, such as carrying eggs and delivering milk in glass bottles, and none of them worked out. Mr. Bump is upset and doesn't understand why is is Mr. Careful, but really isn't careful, he didn't know where he was going but his memory is quickly restored when he bumps into a tree... and then he promptly falls into a river.