Warner Bros. lays claim to Happy Birthday over a 1935 publishing date by Orem & Forman. Now a documentary filmmaker claims the song was published in 1922 by Clayton Summy Co. Clayton Summy and Mildred Hill never filed a copyright claim for the tune.
http://www.cbc.ca/news/business/happy-birthday-song-copyright-invalid-filmmakers-allege-1.3172074
http://www.cbc.ca/news/business/happy-birthday-song-copyright-invalid-filmmakers-allege-1.3172074