Brennan Huff (Will Ferrell) and Dale Doback (John C. Reilly) are two jobless 40-year olds still living at home whose cosy lives are set to come crashing down when their parents decide to marry - Will they move out and get a place of their own? Or share a room and fight to the death?!

When the boys wreck the boat, Dr Bob is on a downer and its not long before Nancy announces their divorce. In a painful scene, the boys blame themselves and start to cry.
  With the parents both moving out and planning to sell the house, the boys need to grow up. Their insecurities come out again and they have an almighty battle where they both try to bury the other alive.

Next day they go their separate ways and take new jobs - Brennan at his brother's helicopter lease-hire firm and Dale at a catering firm.  They turn their lives around, and Brennan helps organise the large 'Catalina Wine Mixer' event, hiring Dale's firm as they are now recognised as one of the best around.

The Billy Joel tribute band have a fight with a punter, and Brennan is sacked by his brother. Without any music, the event is collapsing until Dr Bob for some reason has a pep talk to Dale and Brennan - saying that he misses his old son, and that he should be himself.

Dale takes to the drums, but the crowd don't like it.  Brennan walks up to the mic and starts to belt out that famous Andrea Boccelli track, and the crowd responds.

The psychiatrist shows up, and she is keen on Brennan - while Dale does the right thing and dumps Alice. The parents get back together again.
  The boys launch their global organisation - Prestige Worldwide - focusing on a karaoke franchise to start with. And the dad transforms his wrecked boat into a new treehouse.

In the closing credits is (finally) something that works when the boys return to the playground for a spoof major fight against the bullies.

To be fair, the extras on the DVD are a lot better than the movie -- "Line-o-rama" shows multiple versions of one-liners, of which strangely they chose the unfunniest for the movie - but also explains a lot about the movie. Having a script to work from is generally a good thing I'm guessing.

Ok, I get it - it's a parody because these 40 year olds are meant to be immature and demanding teenagers, but it still doesn't make it easy to watch - or all that funny. It would work as a short Will Ferrell inspired "Saturday Night Live" sketch, but a whole movie of it?