What Is the “Fat Tiger Effect” and How It Shapes Open‑Source Trust

Today we discuss a fascinating phenomenon called the “Fat Tiger effect.”

In the classic anime Doraemon , the bully character Fat Tiger is despised, but when he occasionally does something good, audiences suddenly view him more favorably.

Conversely, a person known for good deeds who does something bad can have their reputation plummet, as the saying goes, “a hypocrite is scarier than a real villain.”

The term originated from a parody line in the manga Gintama . Although it lacks a solid theoretical basis, the simple example vividly reflects a common psychological phenomenon, which is especially evident in the open‑source world.

Open‑Source “Fat Tiger Effect”

The most classic example is Microsoft’s transformation.

Historically, Microsoft was the biggest enemy of the open‑source community, openly calling Linux a “cancer” and suppressing open‑source projects for over a decade through media, legal threats, and other tactics.

Microsoft’s bad reputation was historically earned. Bad deeds accumulate, making it hard to do good later. — 2012‑10‑02 How could “Microsoft” and “open source” ever be together? — 2014‑06‑11 When will Microsoft ever have a positive view of open source? Never. — 2014‑06‑12

After changing CEOs in 2014, Microsoft embraced open source, open‑sourcing large parts of the .NET stack and actively contributing to the community, though the underlying motive remained commercial benefit.

Microsoft finally got it right, shifting to .NET — 2014‑11‑13 Check last year’s Linux kernel contribution list; Microsoft is already in the top twenty. — 2014‑11‑15 Microsoft, I love you. — 2014‑11‑16 Microsoft finally opened up, changed its ways — 2015‑02‑04

Similar negative cases include Qt’s move to a commercial LTS model, which sparked strong community backlash, and Red Hat’s shift from CentOS to CentOS Stream.

Qt is dead, won’t use it anymore. — 2021‑01‑06 Goodbye to the increasingly closed‑source Qt, hoping for a community version. — 2021‑01‑06

These shifts caused many users to feel betrayed, as the projects were previously marketed as “open, free, and shared.” When they turned commercial, they were labeled as “cutting the community’s lettuce.”

In the frontend world, recent npm supply‑chain attacks amplified these concerns. The node‑ipc package author added a “Peacenotwar” file supporting Ukraine and inserted malicious code for users from Russian or Belarusian IPs, damaging many downstream projects. Another case involved the event‑source‑polyfill package, where the author silently added anti‑war code, causing widespread panic.

These incidents not only tarnished the reputations of the original authors but also raised doubts about the security of open‑source software among enterprises.

One developer on GitHub warned that such events show free and open‑source software can be used as a supply‑chain attack vector, affecting even companies unrelated to politics.

Rational View of the “Fat Tiger Effect”

The core of the “Fat Tiger effect” lies in the gap between expectations and reality. Open‑source projects are often promoted as “free,” creating high expectations. When they become commercial, users feel betrayed.

Supply‑chain attacks like the npm poisoning illustrate how expectations of transparency and safety can be shattered, reminding us that both open‑source and closed‑source software can have security issues.

Ultimately, the “Fat Tiger effect” is a reminder to maintain a balanced, nuanced perspective: the openness of a project does not guarantee its quality, and decisions should be based on whether the software meets our needs, not on moral judgments.