In order, the letters, followed by the creatures for which the letters are the first letter when spelling their names, are YUZZ (Yuzz-a-ma-Tuzz), WUM (Wumbus), UM (Umbus), HUMPF (Humpf-Humpf-a-Dumpfer), FUDDLE (Miss Fuddle-dee-Duddle), GLIKK (Glikker), NUH (Nutches), SNEE (Sneedle), QUAN (Quandary), THNAD (Thnadners), SPAZZ (Spazzim), FLOOB (Floob-Boober-Bab-Boober-Bubs), ZATZ (Zatz-it), JOGG (Jogg-oons), FLUNN (Flunnel), ITCH (Itch-a-pods), YEKK (Yekko), VROO (Vrooms), and HI!

Judith and Neil Morgan, Geisel's biographers, note that most of the letters resemble elaborate monograms, "perhaps in Old Persian".

[5] In the 2008 American animated film Horton Hears a Who!, Zatz-its appear as residents of the Jungle of Nool.

The Vancouver Sun described the "problematic imagery" as "probably the least obvious" of the six books removed from publication.

[8] Kyle Smith of the National Review describes Nazzim as "a proud-looking camel-riding Arab nobleman".

[10] According to an article of Distractify, Nazzim "is a man who appears to be of Middle Eastern descent".