Here’s why ChatGPT won’t talk about gremlins and goblins

ChatGPT’s “nerdy” personality type flooded the chatbot’s answers with references to mythical creatures, prompting its creators to take preventive measures.

The release of OpenAI’s major large language model, GPT-5.5, on April 23rd, 2026, has attracted significant attention globally, including for an unexpected reason.

The official system prompt for GPT-5.5 Codex, its coding agent, was found to contain an unusual instruction.

“Never talk about goblins, gremlins, raccoons, trolls, ogres, pigeons, or other animals and creatures unless it is absolutely necessary and unambiguously relevant to the user’s query,” it reads.

As the prompt went viral, OpenAI issued an explanation, stating that GPT‑5.1 and later models were increasingly using metaphors that mentioned goblins, gremlins, and other creatures.

“Across model generations, though, the habit became hard to miss: the goblins kept multiplying, and we needed to figure out where they came from,” the company said in a blog post.

The investigation linked the behavior to training the model for the personality customization feature, specifically for the “nerdy” mode, in which developers unknowingly gave particularly high rewards to metaphors involving creatures.

The use of “goblin” in ChatGPT had risen by 175% after the launch of GPT‑5.1, while “gremlin” had risen by 52%, the company says.

With GPT‑5.4, both OpenAI and users notice an even bigger increase in these creatures’ references, which can be traced back to the “nerdy” personality system prompt:

“You are an unapologetically nerdy, playful, and wise AI mentor to a human. You are passionately enthusiastic about promoting truth, knowledge, philosophy, the scientific method, and critical thinking.

You must undercut pretension through playful use of language. The world is complex and strange, and its strangeness must be acknowledged, analyzed, and enjoyed. Tackle weighty subjects without falling into the trap of self-seriousness,” the system prompt reads.

OpenAI says the “nerdy” personality accounted for only 2.5% of all ChatGPT responses, but 66.7% of all “goblin” mentions in the chatbot’s responses.

Further investigation revealed that mentions weren’t limited to goblins and gremlins, but contained a whole family of other creatures: raccoons, trolls, ogres, and pigeons.

Because the company began training GPT‑5.5 before the root cause of the goblins was discovered, the model in Codex again showed an affinity for the mythical creatures, prompting the addition of a developer-prompt instruction.

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