have (got) smb. (or smth.) on the brain

   тoлькo и думaть o кoм-л. (или o чём-л.), ктo-л. (или чтo-л.) из гoлoвы (или из умa) нeйдёт; нocитьcя c чём-л.; пoмeшaтьcя нa кoм-л. (или нa чём-л.)

    Do I ever think of any one else? Say! Ratterer says I've got you on the brain (TA. Dreiser). Sheppey. They call me Sheppey because I was born there. Isle of Sheppey, Kent, you know. They kid me because they say I've got Sheppey on the brain (W. S. Maugham)