Howling:Why is earth so vulnerable?

The Howling → Why is earth so vulnerable?

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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. 87.102.91.126^{talk to me} 19:38, October 7, 2013 (UTC)