Riddle #4: Dr Who and the invisible man

The actors who have played Dr Who were:

William Hartnell (1963–1966)
Patrick Troughton (1966–1969)
Jon Pertwee (1970–1974)
Tom Baker (1974–1981)
Peter Davison (1982–1984)
Colin Baker (1984–1986)
Sylvester McCoy (1987–1989, 1996)
Paul McGann (1996)
Christopher Eccleston (2005)
David Tennant (2005–present)

Eccleston left and was replaced by Tennant.

How is it that one could rightly say that Dr Who became The Invisible Man?

Riddle #3: Making it add up - Solutions

Solution 1
Change the first + to a 4 by a single oblique stroke of the pen or pencil
Solution 2
Change the second + to a 4 by a single oblique stroke of the pen or pencil
Solution 3
Add a stroke to the equals symbol to create the universal not equal symbol.

Riddle #3: Making it add up

The equation above (5+5+5=550) is incorrect. Write it down for yourself on a piece of paper. How could you correct it by the addition of a stroke of a pen or a pencil; just a single straight line?

There are 2 ways, maybe 3 ways, but certainly not 4 ways.

Riddle #2: What are you so good at, you can do it in your sleep?

gnihtaerB