A person has created the code so that Windows 95 can be installed and run on an Apple Watch, but it was not an easy task.
That person, Nick Lee, posted just how he accomplished this project on his Medium page. He points out that the hardware inside the Apple Watch (a 520 MHz processor, 512MB of RAM, and 8GB of internal storage) should be able to handle the 26 year old Windows 95 with ease. In practice, however, it took a lot of effort. We won't go into the programming details but let's just say it is definitely not as simple as just installing the OS on the smartwatch. He even set up a way to keep the smartwatch's crown going, so it would not fall asleep during the process.
The final result can be seen in Lee's video above. As he points out, Windows 95 still takes an hour to boot on the Apple Watch due to the fact that the OS is running on an emulator, but it does work, sort of.