from left to right:

top row - 1. William Hartnell, 2. Patrick Troughton, 3. Jon Pertwee

second row - 4. Tom Baker, 5. Peter Davison, 6. Colin Baker

third row - 7. Sylvester McCoy, 8. Paul McGann, 9. Christopher Eccleston

bottom row - 10. David Tennant, 11. Matt Smith, 12. Peter Capaldi

First Doctor (William Hartnell) and Second Doctor (Patrick Troughton)

Third Doctor (Jon Pertwee) and Fourth Doctor (Tom Baker)

Fifth Doctor (Peter Davison) and Sixth Doctor (Colin Baker)

Seventh Doctor (Sylvester McCoy) and Eighth Doctor (Paul McGann)

Ninth Doctor (Christopher Eccleston) and Tenth Doctor (David Tennant)

Eleventh Doctor (Matt Smith) and Twelfth Doctor (Peter Capaldi)