The amusing title drew my eye to it and pleasingly the tone of the film is perfectly summarised by the rather tongue in cheek title. You see this is not in any way a serious exploration of the theory behind parallel worlds but rather a look at how they operate within science fiction in films and television. As you would imagine, it is incredibly geeky but mostly it more or less keeps the humour right for the casual viewer who, for example, enjoys Star Trek but does not dress as Kirk at the weekend. What this means is that we get a quite cheeky look at the conventions of the genre and get to poke gentle fun at them.
On the downside, there clearly isn't enough general material to fill an hour so we do spend too much time looking at, say, one specific episode of Buffy, which does rather go away from the concept of the film and ends up talking specifically about that episode. This is a little offputting if you have not seen that specific episode but is still distracting enough. Here and there we get some contributions that hint at how important and serious all this stuff is, but mostly this is kept in check and the film never goes off rambling about how if you really understand Kirk then you'll learn all the lessons you'll ever need to about how to live life etc.
Overall then a clearly tongue in cheek film that will be enjoyable to most sci-fi fans who are able to laugh at the genre they enjoy.