Adaptive Automaton

Oracle Text

As Adaptive Automaton enters the battlefield, choose a creature type.

Adaptive Automaton is the chosen type in addition to its other types.

Other creatures you control of the chosen type get +1/+1.

Card Rulings

9/22/2011 The choice of creature type is made as Adaptive Automaton enters the battlefield. Players can’t respond to this choice. The bonus starts applying immediately.
9/22/2011 You must choose an existing _Magic_ creature type.
9/22/2011 Even though Adaptive Automaton is a Construct, other Construct creatures you control won’t get +1/+1 (unless you chose Construct as Adaptive Automaton entered the battlefield).