Character Analysis
Oskar Rie was the family pediatrician and one of Freud's oldest friends (source).
One scholar thinks that Rie is the "Otto" who appears in Freud's Dream of Irma's Injection (source). In the dream, Rie doesn't appear in a particularly good light—in fact, the dream-contents depict him as someone who is thoughtless, careless, and not as thorough as he should be (2.1.27, 41, 42).
Why does Freud's Dream of Irma's Injection show Rie in such poor light? As Freud explains in his analysis of the dream, Rie's appearance as a thoughtless and careless doctor makes Freud look good by comparison. Freud realizes that the Dream of Irma's Injection was a wish-fulfillment: it said to him, "I was not to blame for Irma's pains"—"Irma's pains had been caused by Otto giving her an incautious injection of an unsuitable drug—a thing I should never have done" (2.1.44).
As with the appearances of Freud's other family members, friends, and colleagues, Rie's presence in The Interpretation of Dreams tells us very little about the real-life man. Instead, we see how Freud's dreaming mind used Rie in order to make the dreamer feel better about himself.