In chapter fourteen of John Boyne's The Boy in the Striped Pajamas, Bruno is talking to his sister when he accidentally mentions that he has a friend (which he does). Immediately he can tell he should not have mentioned that fact to Gretel, and he tries to cover his error by lying and claiming it is an imaginary friend. As he says it, he tries to look embarrassed and ashamed of being nine years old and still having an imaginary friend.
The problem is that Bruno is not really embarrassed because Schmuel is not imaginary, so he has to think of other embarrassing things that have happened in his life so he can muster up some embarrassment to convince Gretel. He struggles for a bit and then remembers
the time he had forgotten to lock the bathroom door and Grandmother had walked in and seen everything. He thought of the time he had put his hand up in class and called the teacher 'Mother' and everyone had laughed at him.
Bruno also remembers one time when he was trying to do a fancy trick on his bicycle to show off for a bunch of girls and he ended up not only falling off the bike but cutting his knee and crying.
One of them must have worked, because suddenly Bruno looks quite embarrassed and Gretel believes him.