Other mistake: When Harry is talking with Arthur Weasley at the Leaky Cauldron, the number '301' (colored in white) digitally pops up right underneath the wanted poster. The composite people neglected to remove it. This mistake occurs in a DVD widescreen version, and not visible in all versions. (This is not referring to Sirius Black's number '390' written on the paper that Sirius holds in the poster). (00:16:50)