The goblins were funny at first, but the increasing number of employee reports became concerning.

The first time we clearly saw the pattern was in November, after the GPT‑5.1 launch, although it may have started earlier⁠(opens in a new window). Users complained about the model being oddly overfamiliar in conversation, which prompted an investigation into specific verbal tics. A safety researcher had experienced a few “goblins” and “gremlins” and asked that they be included in the check. When we looked, use of “goblin” in ChatGPT had risen by 175% after the launch of GPT‑5.1, while “gremlin” had risen by 52%.

At the time, the prevalence of goblins did not look especially alarming. A few months later, the goblins came back to haunt us in a much more specific and reproducible form.

With GPT‑5.4, we and our users⁠(opens in a new window) noticed an even bigger uptick in references to these creatures. That triggered another internal analysis and surfaced the first connection to the root cause: creature language was especially common in production traffic from users who had selected the “Nerdy” personality. “Nerdy” used the following system prompt, which partially explained the quirkiness: