Once users get accustomed to a site they form an idea of its capabilities and limitations–YouTube can play videos, Facebook can show pictures and messages from friends and so on.

But, assuming these sites’ coding teams are capable, these limitations are purely user-imagined. If Facebook wanted, they could change their color scheme to fuschia and brown and have GIFs of puppies on every page.

Hopefully the fuschia and brown shift doesn’t happen. But here are some instances of sites bending their limitations in cool ways.

The white-out maker Tipp-Ex partnered with YouTube to create a video where users can control the plot by clicking and typing within the video.

Old Spice recently released its Old Spice Muscle Music video, which features Terry Crews playing instruments with his muscles. After the initial minute, an interactive music player displays, still within the Vimeo player, that lets you record your own muscle music.

Googling “Do a barrel roll” will cause your screen to do a barrel roll–a tribute to a meme from the video game Firefox.

In all of these instances, users were unaware that the sites were capable of such maneuvers, which made their reactions much more enthusiastic. Of course, once these easter eggs become common, their entertainment fades. But do it right and you have potential for serious eyeballs.