Reverend Frederick Douglas Kirkpatrick (1933-1987) was a civil rights activist and folk singer, sometimes known as Brother Kirk. Kirkpatrick worked as a director in various human rights organizations, including the Poor People's Campaign for Jobs and Income in Washington, D.C.

In 1974, Kirkpatrick and Pete Seeger recorded a Sesame Street album titled Pete Seeger & Brother Kirk Visit Sesame Street, singing with Big Bird, Oscar and the Kids. The album featured traditional folk songs, as well as one topical song, "The Ballad of Martin Luther King."

Kirkpatrick appeared on the Street in episode 0719, which aired in January 1975. In this appearance, he sang "The Animal Song" with Sam the Machine and the Kids.