piggy in the middle
noun /ˌpɪɡi ɪn ðə ˈmɪdl/
  /ˌpɪɡi ɪn ðə ˈmɪdl/
 (also pig in the middle)
 (both British English) (North American English monkey in the middle)
- a children’s game where two people throw a ball to each other over the head of another person who tries to catch it过顶传球(儿童游戏,由两人抛传球,中间一人争抢) 
- a person who is caught between two people or groups who are fighting or arguing(被夹在中间而)左右为难的人