jQuery replace text of element on hover

add another function to the hover event like this:

$('.btn').hover(function(){
    $(this).text("I'm replaced!");
}, function() {
    $(this).text("Replace me please");
});

Link for demo

$('.btn').hover(function() {
    // store $(this).text() in a variable     
    $(this).text("I'm replaced!");
},
function() {
    // assign it back here
});

This should do the trick

$(function(){
  var prev;    

  $('.btn').hover(function(){
  prev = $(this).text();
      $(this).text("I'm replaced!");
  }, function(){
      $(this).text(prev)
  });
})

$('.btn').hover(
    function() {
        var $this = $(this); // caching $(this)
        $this.data('defaultText', $this.text());
        $this.text("I'm replaced!");
    },
    function() {
        var $this = $(this); // caching $(this)
        $this.text($this.data('defaultText'));
    }
);

you could save the original text in a data-defaultText attribute stored in the node itself so to avoid variables