Player connection isn't a variables, it's a function, and that function is:
function GameConnection::OnClientEnterGame(%this)
{
echo("Lol, hai");
Parent::OnClientEnterGame(%this);
}
But, a problem, as that echo is a client command, it will be directed to whoever is running the code, which would be you. The host, you would have to send the command to the client, with commandToClient, although i don't know if you can do that with echo, but echo is boring anyway.
commandToClient(%this,'messageBoxOk',"lol","hai u just spawned lol");
So if you put that instead of the echo("Lol, hai"); bit, you get that message when you join. The parent::blah bit just runs the rest of the function.