The indignant merchant asked his customer what made him so sure that the item was a fake. The customer replied that, first of all, he was Leonardo DiCaprio, and that, secondly, he hadn't signed it!
[The shopkeeper promptly took the poster down. (According to PSA/DNA Authentication Services, only six per cent of autographed Beatles memorabilia is authentic.)]
[Titanic-inspired Leomania was so widespread that as late as 2001, 28 barbers in Kabul were arrested by the Taliban for giving kids DiCaprio haircuts. Titanic reportedly resembles a phrase meaning "let's have sex" in Arabic.]