Backbone collection filter
Reviewing code for coolness is a first ;)

Some observations:


initialize : if really all you want to do there is Hello World, then you should take it out. initialize is meant for initializing your model with answers.
getCorrect and getWrong are short one-liners that are called once, you should inline them
arr1, arr2, coll and even result are pretty terrible names, how about correctAnswers, wrongAnswers, answers and not creating coll since you could return the results of new AnswersCollection immediately.
The most serious problem though is that you are not declaring the prior mentioned variables with var, that is bad.


Also, from a coolness perspective, braces on their own line is where it's at.

I would counter-propose this:

var AnswersCollection = Backbone.Collection.extend(
{
    model: Answer,

    randomSet: function(correct, wrong) 
    {
        var correctAnswers = _.sample(this.where({correct: true}), correct),
            wrongAnswers = _.sample(this.where({correct: false}), wrong),
            answers = _.shuffle(correctAnswers.concat(wrongAnswers));

        return new AnswersCollection( answers );
    }
});