Sylvester McCoy's umbrella had a question mark incorporated into the design of its handle.
The phrase "Doctor who?" and similar ones have appeared as a running joke throughout the run of the series, including a "Doctor Whoever-you-are" from Tegan when she first met the Doctor in "Logopolis." The only time the Doctor has actually been referred to as "Doctor Who" in the series was in a First Doctor story, "The War Machines" (1966); this is acknowledged as a mistake. The title of the series comes from the first story, in which hapless humans Ian and Barbara assume his name is Dr. Foreman (not too outlandish an assumption, as their student Susan Foreman calls him her grandfather) and he responds, "Doctor who?" Recent episodes, leading up to the 50th anniversary special, make much of the fact that we do not know the Doctor's real name, making the question "Doctor who?" part of the actual storyline.
There were two Doctor Who movies in the 1960s, starring Peter Cushing as a character who is actually called "Doctor Who," but they are considered non-canon.