"Irretrievable hippopotamus"

From Janet Malcolm's collages (NYRB) based on "the papers of an émigré psychiatrist who practiced in New York in the late 1940s and 1950s":

Test words for dysarthria

Royal Artillery
Methodist Episcopal
West Register Street
[crossed out]
Massachusetts Constitution
Righteous Retribution
Irish Constabulary
Irretrievable Hippopotamus

And then there was also this (under "ouch ouch disease"):