THIS IS 40
As a huge Knocked Up fan I was happy to hear Apatow was doing a spinoff film. Though I wish that Rogen and his friends were back (only Jason Segal and Charlyne Yimakes return, Rogen's character briefly mentioned) there was enough to look forward to as Rudd, Leslie Mann and the two girls were funny and characters you wanted to see more of. Plus the additions of Albert Brooks, Robert Smigel and Chris O'Dowd fill in quite well.
Pete and Debbie turn 40 in the same week but Debbie is one of those women that lies about her age and she's quietly turning 38. Pete is having a big party at the house and is mentioned throughout the film, so we're expecting that this will happen later in the film. Debbie decides that the next 20 years will be the best years of their lives and creates a list of things they'll do to make life even better. The exact opposite happens and adds more stress the the family's problems.
This is a spinoff, so it isn't a comedy like Knocked Up. It still has a few raunchy moments but it has a lot more drama. There are parts that do drag and you feel that Pete's birthday party should've happened by now. There is a bit of character development, the change isn't as great as Rogen's was in Knocked Up. Like Knocked Up there are some celebrity cameos and "Friends of Apatow" in minor roles. There is still plenty of yelling and arguing but this time the grandparents and kids get in on it. Megan Fox steals some scenes, Segal is great as always but left you feeling the film could've been better if Jay Baruchel, Jonah Hill, Martin Starr, Seth Rogen and yes Katherine Heigl were in the film. Just given the history, chemistry and that you would expect them to show up to Pete's birthday party. Kind of had the feel of the fourth Indiana Jones film where they write out Henry Jones Sr., introduce new friends and ignore Short Round and Sallah.
Overall the good outweighs the bad. You may see yourself in some of the characters be it Pete, Debbie or the kids and maybe even Pete's Dad played perfectly by Brooks. If you were a big Knocked Up or Paul Rudd fan I would say see it in theatres or perhaps wait until the DVD which will surely have an hour worth of deleted and alternate takes along with a blooper reel. Stay during the credits for an extended blooper and see how many times you laugh.