Howling:Why is earth so vulnerable?

Why is earth the most invaded/visited planet in the universe? Has there ever been an explanation. The only in universe reference I know of is when the second doctor is on trial by the time lords, he says earth seems more vulnerable than others as a reason for why he had had frequent visits to it.--Coop3 ☎  18:56, October 5, 2013 (UTC)

Do we know it is the most invaded/visited planet? I thought that was David Walliams' character's planet. 87.102.91.126talk to me 19:38, October 7, 2013 (UTC)

Yeah, think of the planet whose anthem/motto is "All hail (insert name here)", or something. Earth fights back, they plant trees along the roads so invading armies can walk in the shade. —BioniclesaurKing4t2 - "Hello, I'm the Doctor. Basically, . . . run." 22:58, October 7, 2013 (UTC)