Harold first appears in the strip from December 24, 1983, but is first referred to on December 16 of that same year. In the storyline in which he first appears, Sally is in a Christmas play in which her only line is "Hark". Sally insists that after her line, a person named Harold Angel will sing. Charlie Brown and Linus both assume that she somehow misunderstood or misheard, and that no child named Harold Angel is supposed to sing. After the play, when Sally messes up her line by saying "Hockey stick" instead of "Hark", Charlie Brown is proven wrong about Harold Angel not existing when a small boy named Harold Angel comes over to the Browns' house to comfort Sally on her bungled line reading. He appears about 5 months later on May 20, 1984, where he tries to take Sally to the movies.
The series of strips which introduced Harold Angel were later adapted into one of the shorts in the episode "Sally's Sweet Babboo" from the second series of The Charlie Brown and Snoopy Show and one of the segments of the 1992 animated TV special, It's Christmastime Again, Charlie Brown.