
Quick answer — Tomo Shigematsu voices O'Brien in Halo Legends, Udon in NARUTO: Honoo no Chuunin Shiken! Naruto vs Konohamaru!!.
Tomo Shigematsu voices O'Brien (Halo Legends), Udon (NARUTO: Honoo no Chuunin Shiken! Naruto vs Konohamaru!!).
O'Brien is voiced in Japanese by Tomo Shigematsu.