Each of the persona poems in this collection is written in the voice of a historical figure, contemporary cultural icon, or well-known literary character. The poems are written in the lipogram form, a constraint in which certain letters of the alphabet are deliberately omitted from the work. In Impersonations, Zimmermann has limited himself to the letters contained in the name of each persona; for instance, the poem "Sigmund Freud" uses only the letters s, i, g, m, u, n, d, f, r, and e. Zimmermann has worked wonders with these severe limitations, producing poems that are lyrical, witty, and smart.