I once had an old Nokia cell phone, and I knew the menus by heart – which came in handy when a friend changed my language settings to Arabic. With all the menu options moving from right to left, it took me more than a few hours of screwing around to change the settings back.
You can pull the same shenanigans on your coworkers. Forget pulling a phone prank, and go for Google instead. When someone leaves a computer unattended, simply go to Google’s home page and click on Preferences. Then choose your poison – leaving a work computer in Klingon might be a good choice. Yiddish is also appealing – or go for Thai and leave the user utterly baffled.
Somehow the language settings are difficult to change back – but that could just be the fact that nothing looks the same in Klingon.
To fix the language back after the prank just click on the "Google.com in English" link below the search box on the main Google page.