From LedHed's Wiki
You can Rick Roll your users with one simple tool, the 'at' command.
Example:
at \\REMOTE_HOST 15:31 /INTERACTIVE "c:\Program Files\Internet Explorer\iexplorer.exe" http://your-fav-rickroll-site.com
Make sure to set the time option to something in the future, otherwise the task wont run as its time is in the past.