IMAGINE a world where the characters from Sesame Street have grown up and it's all gone a bit wrong - Cookie Monster is a porn addict and Bert's in love with Ernie.

If you can instantly visualise what that would be like, either you need to seek professional help or you've seen Avenue Q.

The Avenue Q monsters have been shouting at Londoners from tube station escalators since 2006, but it's one of those plays that has still escaped many theatre-goers and, really, probably won't appeal to your average thespian or musical lover.

Aimed more at the South Park generation, this tale of creature discomfort is set in a poor housing block in New York, Avenue A is the nice area and, well, by the time you get to Q the standard has dropped.

It follows the story of Princeton, a man in his early 20s looking for his purpose in life after getting his degree in English. Having lost his first job before even starting his first day, he gets led astray by the Bad Idea Bears - two Care Bear-alikes offering helpful suggestions like "buy beer" and "why not hang yourself " in a horribly cheery tone.

It's not all bad for the young graduate, he falls in and out of love with Kate Monster and is also accosted by the local cabaret singer/tart.

All of the characters on the street have their own problems, one is gay and in love with his straight flatmate, one has a powerful compulsion to look at adult material on the internet and another is getting married to a harsh, controlling therapist.

However, none are more tragic then their landlord/caretaker, Gary Coleman who seems to have been picked on by the writers somewhat unnecessarily. Gary, is based on the child star of US sitcom Different Strokes. There are several gags at the star's expense, if the audience is in any doubt of who he is meant to be, these are immediately dispelled by his opening speech: "Try having people stopping you to ask you 'What' cha talkin' 'bout, Willis?' It gets old".

Despite having nothing to do with the Jim Henson workshop, the puppets do have a very Sesame Street or Muppet quality - they look amazing with several puppets per character all given different expressions and used as required.

However, unlike the adventures of their small screen counterparts, you can see their pupeteers. This is initially quite off-putting and you never stop noticing them. However, the acting and voices are so good, they only add to their character's value. The production looks even stranger with the addition of several of human characters. Undoubtably, Avenue Q's biggest strength lies in the fabulously crude songwriting, ditties such as: The Internet Is For Porn, and You Can Be As Loud As The Hell You Want (When You're Makin' Love) are horribly catchy and it's worrying when you find yourself belting out "Why you think the net was born? Porn, porn, porn" on the tube home.

Despite the cute-looking puppets, it's not one for the kids, there's even a puppet sex scene to endure and if easily offended then it's probably better to stick to more mainstream musicals.

If you like to be disgusted, are looking for your purpose in life or spend too much time surfing for 'entertainment' on the web then you may just identify with one or two of the characters. [25cf] Avenue Q is on at the Noel Coward Theatre, St Martin's Lane, WC2N, Monday-Saturday (two performances Friday and Saturday).

Tickets range from £10-50 and are available in person from the box office, by calling 08444 825 141 or via www.avenueqthemusical.co.uk