Gist which shows "unexpected" behavior that when I unshift data back on the source I get no call of "_read".

unshift_to_source_stream.js

var stream = require('stream');

var rOne = new stream.Readable();
var rTwo = new stream.Readable();

rTwo.isBody = false;
rTwo.source = rOne;

rOne._read = function() {};

rTwo._read = function() {
    var chunk = this.source.read();

    if (chunk === null)
        return this.push('');

    if (!this.isBody) {
        this.isBody = true;
        this.source.unshift(chunk);
    } else {
        this.push(chunk);
    }
};

rOne.on('readable', function() {
    rTwo.read(0);
});

rTwo.on('readable', function() {
    console.log(rTwo.read().toString());
});

rOne.push(new Buffer('Hello'));