Apparently this song, from Sesame Street, was the inspiration for Andrew Bird's songs "I" and "Imitosis." Originally, the various permutations of the line "we're basically alone" in Bird's songs was "we all live in a capital I" but Sesame Street decided against allowing the use of the lyrics.
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And for reference, here is Andrew Bird's "Imitosis":
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Edit: I notice that at least one other Andrew Bird song references the Capital I, and this one sort of has the opposite message as "I" and "Imitosis." "Skin Is, My"--a love song if there ever was one--proclaims (regarding his love):
"let it be printed on every t-shirt in this land / on the finest of cottons and the hippest of brands / in bolder letters than the capital I / it's the only thing it's the only thing"