The title is a reference to The Outer Limits: I, Robot (1964). It had a similar story of a robot believed to have evil intentions but as the story progressed, he was discovered to be very human with many human ideals. The title is also a reference to Isaac Asimov's short story collection I, Robot, which dealt with similar themes of a single unit of a collective consciousness discovering free will and identity.
Jonathan Del Arco (Hugh) was a fan of The Original Series while growing up, and jumped at a chance to be on The Next Generation. He had auditioned for the role of Wesley Crusher, but when it was given to Wil Wheaton he was so disappointed that he refused to watch "The Next Generation" until he got the chance to guest star on it. He joked that prior to taking the assignment, a friend warned him that he would be asked about it for years afterwards, which indeed proved to be the case.
This episode establishes that Borg are designated by numbers, in relation to small groups (ie, Third of Five, Seven of Nine, etc.). Hugh's designation, "Third of Five," is different from other Borg names (such as Seven of Nine) in that he uses the ordinal ("third") rather than the cardinal number ("three").
When one of the other Borg interfaces with Hugh (having plugged into his arm), the accompanying sound effect seems to include five characters of Morse code. It sounds like 'ECAGE', though the fourth character is somewhat indistinct (and possibly the second).
This was the first Borg episode not to be scored by Ron Jones. Instead, the composer is Jay Chattaway, who would compose "Descent" and "Descent, Part II", the last episodes of The Next Generation to feature the Borg.
While the audience was not given a good glimpse of the ship itself, the Borg scout ship made its first and presumably only appearance in this episode, though it is possible that the Borg probe and some Borg spheres could be considered scout ships.
This episode marks another instance of Guinan using the term "scattered throughout the galaxy", in reference to her people. Other usages of the term were in the episodes "Q Who", and "The Best of Both Worlds".
The trivia item below may give away important plot points.
The aftermath of Hugh's rejoining the Collective is revealed in "Descent" and "Descent, Part II". At the beginning of the Descent two-parter, Admiral Alynna Nechayev criticizes Picard's decision to revise the invasive program from the original plan. Hugh would also appear in the latter episode. The concept of Borg individuality is explored at length on Star Trek: Voyager with the character Seven of Nine.