"Nabeshin" is the well-known nickname of anime director, Shinichi Watanabe. Watanabe himself is notorious for inserting himself into anime using his character, Nabeshin. He is the Deus Ex Machina of Excel Saga and a main character in Puni Puni Poemi, and while he does not appear explicitly in Nerima Daikon Brothers, it is almost universally known that the "rental guy" character is one of Nabeshin's incarnations as he, like all of Nabeshin's roles, is voiced by Brett Weaver in the English dub.
Additionally, he made a brief appearance in episode 24 of Yamato Nadeshiko Shichi Henge, and he is also the narrator in "The Road to Becoming a Lady" of the same series. Nabeshin also appears in one episode of Hayate the Combat Butler, and has a 1-frame appearance as a mechanic in Eyeshield 21, episode 16.