Rumpole has a penchant for giving literary or historical nicknames to friends and foes. His wife Hilda's moniker, "She Who Must Be Obeyed," was originally applied to the title character of H. Rider Haggard's novel "She." Phyllida Trant Erskine-Brown's nickname, "Portia," is from William Shakespeare's "The Merchant of Venice." Samuel Ballard is dubbed "Soapy Sam" after Bishop Samuel Wilberforce', who is now best remembered for debating Thomas Huxley over Charles Darwin's theory of evolution, but regarded in his own time as rather a slick operator. He calls Judge Graves the "whited sepulchre", a Biblical allusion (Matthew 27).
Rumpole was quoted twice during the O.J. Simpson trial. Direct reference was made by a member of the prosecution stating "As Rumpole would say, it all comes down to the blood." A more subtle reference occurred when a defence attorney stated to the Judge that they were getting "a case of premature adjudication", a phrase Rumpole often used.
Horace Rumpole was originally given a moustache for the Season 1 episodes that took place prior to 1974 to give him a more 'retrospective' look. He was clean shaven for the stories set in 1974 and later, and remained so throughout Season 2. For Rumpole's Return (1980) and the remainder of the series, the moustache returned. A possible reason for this was the caricatures of Rumpole in the series' title sequence and novel tie-ins depicted him with the moustache (despite him not having one at all in Season 2), so it was brought back to bring his look in line with the popular image of him.
David Yelland played Rumpole's 17-year-old son Nick in the first episode, despite being 31 at the time. He first appeared in the original BBC, Play for Today,' "Rumpole and the Confession of Guilt" (1975) playing a recently graduated, 23 year-old Nick.