Snoopy, Come Home (movie, 1972)

When Snoopy receives a letter from his original owner Lila, he goes to visit her in the hospital while Charlie Brown and the gang are on the lookout for him. Suddenly, Snoopy feels that he must go live with Lila, but must say goodbye to all his friends. In his adventure to the hospital, he encounters numerous "No Dogs Allowed" signs, an annoying little girl who desires to keep him, and more!