The First Doctor was given his walking stick by Kublai Khan. The Tenth Doctor at first claims he obtained it in an unchronicled adventure involving Oscar Wilde and "midget assassins", but he later admits it was a ruse to trick "Martha."
The Forgotten was a comic book mini-series produced by the American company IDW Publishing in the fall of 2008, following on from its initial Doctor Who title Agent Provocateur.
This was the first officially sanctioned spin-off to feature all ten (at the time) of the Doctor's incarnations.
It was collected and reprinted as the graphic novel The Forgotten in April 2009.
Due to a printing error, the dialogue balloons on Page 1 of Issue 6 were left blank. The absence of the dialogue had caused confusion over whether the villain was meant to be the Meta-Crisis Tenth Doctor or the Valeyard, since most references to it were on this page (although the Doctor refers to the villain as the Valeyard on a later page). Tony Lee posted the missing dialogue on IDW's web forum , and the dialogue was fixed in the trade paperback release.
The fact the villain takes the form of the Meta-Crisis Doctor, and refers to himself as the Valeyard, added credence to the theory that the Meta-Crisis Tenth Doctor could be destined to become the Valeyard. The Doctor, however, laughs at the idea. Until such a time as a connection is actually made, the fact the villain chooses "the Valeyard" as his alias means that, regardless of his appearance, the villain being impersonated here is indeed the Valeyard.
During the First Doctor's vignette, presented in monochrome as a reference to the early seasons of the series being aired as such, the Doctor hopes the TARDIS team doesn't end up in an Aztec temple. The Doctor and his companions did this in TV: The Aztecs.