Who stands behind this anime series and what they have in common ?

1.Ghost in the Shell - 1995

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2. Cowbody Bebop- 1998

 3.Witch hunter Robin 2002

4.Samurai Champloo 2004-2005

5.Ergo Proxy - 2006

 What is the  common point between the 2 and 4 anime or between the 3 and 5 one and the 1 and them all ?

Atmosphere , characters ,  did it happen to you to look at one anime and to find traits of other character in it , did you ever thought that it could have brothers  born form the same thought or hand ?