Here is a collection of JavaScript bookmarklets which you can use to vanquish your enemies (or at least mildly amuse them).

You can try them all out on the project home-page.

Some are also available as User Scripts, which are supported natively in Google Chrome, and can also be used in other browsers with the help of a browser extension (e.g. Greasemonkey for Firefox). The User Script versions have better prank potential, because once installed they will run automatically on every page that the victim visits, whereas the bookmarklets must be manually clicked in order to run.

I have tested these scripts in Google Chrome, Firefox and Safari, they should also work fine in Opera and maybe in Internet Explorer 9 and above.

This script immediately turns a web page upside down, not too subtle but guaranteed to have an impact.

User Script

This script turns every image on the page upside-down.

User Script

This script makes small adjustments to the orientation of various elements on the page, giving it a nice 'broken' look.

User Script

Replaces all images on the page with a picture of teen heartthrob Justin Bieber

User Script

This script does nothing until someone presses a key on keyboard or moves the mouse, then it rotates the page 180°. After you run the script there is a 5 second pause before the trap is activated.

This script replaces any text that the victim enters with the words 'I like frogs'

User Script