I want you to be my Pet.

Being a pet of a higher player in war.. If you can't win a attack in war that results in a new star,  you may be asked to be a pet.. That means you will attack a higher level players attack before him,  to find traps and bombs and teslas on the base that he is attacking.

You ask why should I  do that for a high level player?  Consider it pay back for all the max troops you received from them.  Because you are part of the same team,  being a pet usually results in getting troops you request faster and a favor down the line..