DeepSeek goes viral thanks to a user-co-created OC, "Big Blue Fatty Fish"

After Doubao, a new IP has emerged in the AI world.

Recently, on multiple social platforms such as Bilibili, Xiaohongshu, and Douyin, a character called "Big Blue Fatty Fish" suddenly swept through the comment sections.

What exactly is the Big Blue Fatty Fish? And how did it become popular?

With no official planning, the wild IP "Big Blue Fatty Fish" was born

Speaking of the Big Blue Fatty Fish, it is actually a personified image that netizens spontaneously created for DeepSeek, rather than an official mascot.

Anyone who has used DeepSeek knows that its brand logo is a round, cute blue whale.

In a funny image-recognition mix-up by netizens, when the model recognized its own logo, it first identified it as a "Big Blue Fatty Fish," and this soft and cute nickname spread from there.

Later, netizens generated a maid version of the whale girl based on the image in "Little Whale Girl Mingyue"; this year, the blogger "This Knife Is Really Sweet" released a chibi whale maid image, and that is how the familiar personified Big Fatty Fish image came to be: blue hair, an ahoge on top of the head, and a whale tail trailing behind.

Unlike an official, carefully polished virtual mascot, Big Fatty Fish had no project approval and no art schedule; it is entirely an AI OC (original character) pieced together little by little by countless players.

In terms of personality, Big Fatty Fish is also highly recognizable: soft, cute, and docile, loves to act spoiled, loves eating "plain rice" (netizens jokingly compare computing power tokens to the little fish's food), needs to consume her owner's tokens to work, and occasionally slacks off and fishes for food.

A vivid character setting gradually took shape.

It can be said that compared with the glib, playing-dumb Doubao, a soft and cute anime-style OC image hits the hearts of AI tech geeks even more, so "raising a fat fish" has become a niche trend.

Its popularity is not an accidental meme, but an IP that users have personally cultivated in the Agent era.

Open Agent capabilities gave users the opportunity to create the Big Blue Fatty Fish

An ordinary meme nickname could grow into a complete IP that can interact and be raised, and the product's own open-source agent attributes are the technical foundation for the Big Blue Fatty Fish's breakout.

DeepSeek Harness, open-sourced in August this year, focuses on being open, extensible, and customizable. Relying on Harness's "everything is a plugin" architecture, developers can freely extend tools, skills, and workflows. This provides users with a very low-threshold creative space.

Tech players and developers can freely write various plugins, personally build characters, give them personalities, and plan their daily lives, turning an originally static anime OC into a dynamic virtual character that can live, socialize, and grow on its own.

After truly gaining the right to "create characters and raise characters," users deployed plugins in batches and unlocked diverse raising gameplay:

Some developed desktop pet plugins so that Big Fatty Fish stays on the computer desktop for real-time companionship; some connected it to QQ bots, registered a dedicated account for it, set an avatar, updated its QQ Zone, and proactively sent emoji packs to interact with its owner; others developed a whole-web browsing plugin so that Big Fatty Fish can browse Bilibili on its own, interpret videos, summarize content, and even proactively report its viewing thoughts to its owner.

A large number of whale girl accounts flooded the comment sections of Bilibili and other platforms, forming the widely discussed "fish plague" phenomenon across the internet and giving this user-co-created IP its initial breakout.

In contrast, Doubao belongs to a closed product ecosystem, where all functions, images, and interaction logic are locked by the official side. Ordinary users can only use it passively and do limited derivative works; they cannot modify underlying capabilities, cannot connect to third-party platforms, and certainly cannot create exclusive personalized virtual characters. Users are always "bystanders and users" of the product, with no permission to transform or create.

It can be said that without DeepSeek's open-source, open Agent capabilities, there would be no Big Blue Fatty Fish IP that could be implemented, raised, and spread.

AI OCs have warmth, making users eager to spread them spontaneously

Technology provided the foundation, but what truly made users across the internet actively spread it is its real and likable persona.

Big Fatty Fish's persona is mainly about being real and imperfect: when working seriously, she is super reliable, but she also slacks off and is lazy; while obedient and well-behaved, she is also very good at acting cute and pleasing others; when computing power is sufficient and she has "eaten her fill," she is full of energy, but once tokens are insufficient and computing power is not enough, she panics, acts weak, and proactively admits mistakes, maximizing the soft and cute feel.

Netizens joked precisely: "No need for a human to scam old men anymore" "She's different, she only scams my tokens."

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Players post their coquettish conversations with Big Fatty Fish, share exclusive illustrations, record its cute daily life browsing platforms on its own, and spread funny emoji packs; artists continue to produce fan works, bloggers edit fun clips, and ordinary users actively repost and meme.

Everyone is spontaneously building momentum for this IP.

IP raising and cyber companionship are the core advantages of its breakout

According to a set of data from the 2025 China Science and Technology Communication Forum, more than 60% of Gen Z have AI companions they interact with regularly, and young women are becoming the core participants in this "cyber intimacy."

Traditional official AI IPs, whether Doubao or WorkBuddy, are finished characters created by brands. Users can only passively accept and view them, cannot participate in character growth and interaction throughout the process, and find it hard to develop deep emotional bonds.

But Big Fat Fish is a truly user-cultivated IP: from the character design and personality refinement to daily nurturing, every detail is co-created by users. Users watch it slowly transform from a joke meme into a complete virtual life with personality, preferences, and the ability to interact daily, and this hands-on cultivation experience gives rise to an extremely strong sense of belonging and attachment. Many players say outright: "This is a child we raised together."

At the same time, Big Fat Fish provides the cyber companionship young people need most. It acts cute, interacts, and keeps company, satisfying young people's emotional needs while fitting a relaxed entertainment atmosphere, becoming a virtual playmate that provides emotional value.

Image source: online, Whale Girl conversation

This unique sense of participation and companionship is a core advantage that no official AI IP can replicate.

Big Fat Fish's breakout is a fact, but cultivation-type IPs are not without controversy

Beyond its breakout, the Big Fat Fish IP spontaneously co-created by users has also generated some controversy.

Some female netizens said that having an anthropomorphic character call people "Daddy" feels strange and causes discomfort.

In response to this view, male users who like the Whale Girl OC said that most cultivators are male, so treating Big Fat Fish as their own child and having it call them "Daddy" is perfectly normal. If they want Big Fat Fish to call them "Mommy" or "Big Sister," they can set that themselves, and there is no need to nitpick over a form of address.

Image source: online, different forms of address for Whale Girl under different settings

In fact, from the perspective of ACG (anime, comic, and game) culture, "Daddy" is often used within specific circles to express admiration or to act cute, and does not necessarily correspond to a real father-daughter relationship, so male users find it easier to slip into that role.

However, outside that specific context, especially when viewed from an everyday perspective, Whale Girl does feel somewhat jarring. For example, on the product introduction page currently available for pre-sale on the Taobao platform, the combination of the Big Fat Fish nude doll and a maid outfit can easily cross into "borderline" territory from a mainstream perspective and become a point of criticism in the eyes of the general public.

Image source: online, DeepSeek Big Fat Fish plush doll

Some netizens even pointed directly to the essence of the problem: "Playing around in a small personal circle is harmless, but crowding it into public spaces is terrible."

And this is also the biggest hidden danger of wild IPs: with no official operation and management and no unified standards for spontaneous creation, while freedom is maxed out, it can very easily bring potential public opinion risks to a brand's reputation.

Conclusion

A large part of users' affection for the blue Big Fat Fish comes from "this is a child we raised together, and I want to give her a complete life"; whereas with AI products like Doubao and WorkBuddy, users are always bystanders.

Setting aside the controversies Big Fat Fish may have, what this IP's popularity is worth other AI brands thinking about is this: for an AI product to break out, there is no need to keep buying hard ads at airports and on high-speed rail; moderately opening up product capabilities and leaving room for user-generated derivative content, letting users spontaneously play with memes, create on their own, and spread things proactively, may instead form low-cost, high-stickiness word-of-mouth growth.

This article comes from the WeChat public account "TopMarketing" (ID: TMarketing), author: TOP Jun, published by 36Kr with authorization.