gistfile1.js

$.when($.Deferred().resolve(2), $.Deferred().resolve(4))
.then(function(a,b) { 
    console.log(a,b) 
}).then(function(a,b) { 
    console.log(a,b) 
});

// prints "2 4" and then "undefined undefined"

$.when($.Deferred().resolve(2), $.Deferred().resolve(4))
.done(function(a,b) { 
    console.log(a,b) 
}).then(function(a,b) { 
    console.log(a,b) 
});

// prints "2 4" and then "2 4", as expected