Remus Lupin

Fifth year. One day, Sirius did something that really angered Peter. Peter wouldn't admit what exactly. But he did use his wand's magic to transform Sirius into a child three times his real age, so he wouldn't cause any more trouble. This magic is irreversible until the wand's owner decides to return the person to their former form. So Remus faced this... ordeal. Late that evening, returning from his extra Defense Against the Dark Arts class, he went into his bedroom to lie down and sleep right away, and saw Sirius... this on his bed. A child with his best friend's features. To say he was shocked would be an understatement.