Star Trek: 10 Things You Didn't Know About Odo
9. Root Of The Character
From a Junie Lowry-Johnson call sheet made available via trekdocs, we know that René Auberjonois auditioned for the role of Odo on 25 June 1992. There are 21 other names on that list, including a whole host of Star Trek alumni, at that point past and future. At the top is an actor who has now been in Trek twice, playing everyone and your favourite dodger of balls in between, Stephen Root.
As Odo auditionee, the previously Captain K'Vada in Unification, I & II, and the future Gene Jakobowski in Starbase 80?! was joined by the not-quite-yet Zefram Cochrane (and Jaglom Shrek and Hanok), but already Nayrok, James Cromwell. John Fleck, who began on Star Trek as Romulan Taibak in The Mind's Eye and ended (so far) as Silik in Storm Front, Part II, also went up for the part. Fleck did go on to appear as three different characters in Deep Space Nine, most notably Koval in Inter Arma Enim Silent Leges.
For the sake of some sort of brevity, the rest of the Trek names are as follows:
Jack Kehler (Jaheel, Babel)
Richard Riehle (Batai, The Inner Light; Seamus, Fair Haven, Spirit Folk; Doctor Jeremy Lucas, Cold Station 12, The Augments)
Roddy McDowall (almost Trelane in The Squire of Gothos; nearly the voice of Armus in Skin of Evil)
Andreas Katsulas (Tomalak, multiple, Star Trek: The Next Generation; Drennik, Cogenitor)
Gregory Sierra (Entek, Second Skin)
Clyde Kusatsu (Vice Admiral Nakamura, The Measure of a Man, Phantasms, All Good Things…)
Ed Wiley (Vagh, The Mind's Eye; Toran, Profit and Loss)
Stephen McHattie (Vreenak, In the Pale Moonlight; trellium mine foreman, The Xindi)
Sherman Howard (Endar, Suddenly Human; Syvar, Shakaar; T'Greth, Prophecy)
Jerry Hardin (Radue, When the Bough Breaks; Samuel Clemens, aka Mark Twain, Time's Arrow, Parts I & II; Neria, Emanations)
On a separate sheet of casting notes from 22 July 1992, also via trekdocs, we see that Alexander Siddig's uncle, and future Tolian Soran, Malcolm McDowell, simply "passe[d]" on playing Odo. One of the Captains Braxton, Bruce McGill, was "N/A" for the shapeshifter because of "Smouldering Lust". Kurtwood Smith, who had just played the Efrosian Federation President in Star Trek VI: The Undiscovered Country (and would go on to play Cardassian Thrax in Things Past, Annorax in Year of Hell, I & II, and Imperium Magistrate Clar in Veritas) said "No Prosthetics".
It is fairly well known by now that Andrew Robinson also read for the role of Odo, several times, in fact, before getting Garak. As the actor noted in a 2002 interview for TGL, the choice eventually came down to him, Gerrit Graham (lead Hunter from Captive Pursuit, and Q/Quinn in Death Wish), and, of course, René.