On Beyond Zebra! is an illustrated children's book by Theodor Geisel, better known as Dr. Seuss. This book fits into the genre of literary nonsense. The young narrator, not content with the confines of the ordinary alphabet, invents additional letters beyond Z, with a fantastic creature corresponding to each new letter. The creatures include favorites such as the Floob-Boober-Bab-Boober-Bubs, large buoyant heads which float serenely in the water. These naturally serve as the example for the letter "FLOOB".
Most of his letters look like monograms of their names. In order, these are named 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(MS) (Vrooms), and HI! (High Gargel-orum). The book ends with an unnamed letter that apparently is a monogram of all 26 letters in the existing Latin alphabet from A to Z, which is fan-named "ABCDEFGHIJKLMNOPQRSTUVWXYZ". It is left as an exercise in naming for the reader.
Some of the animals from On Beyond Zebra appear in the 1975 CBS TV Special, The Hoober-Bloob Highway such as a Jogg-oon, a Sneedle, a Zatz-it, and a Wumbus.
These letters are not officially encoded in Unicode, but the independent ConScript Unicode Registry provides an unofficial assignment of code points in the Unicode Private Use Area for them.