If you haven't seen the film (shame on you!) then Shrek, the ogre, lives in a nasty smelly swamp, which he loves but which is invaded by fairytale characters relocated from Duloc by Lord Farquaad. They want to return to their homes and Shrek wants his swamp back, so they convince him (as he is big and scary) to go and negotiate with Lord Farquaad. Meanwhile, Lord Farquaad has learned of a Princess (Fiona) who is in need of rescue and whom he can marry to make Queen when he becomes King - being lazy (amongst other things) he decides to send Shrek to do the actual rescuing (from the tall tower in the dragon protected castle surrounded by lava) and so the quest begins. Picking up a talking Donkey on the way, Shrek manages to rescue the Princess and starts the return journey with her ... slowly they fall in love but the Princess has a secret she cannot share. Anyway, there is the necessary falling out, the Princess agrees to marry the Lord and Shrek returns to his swamp only to learn that the Princess really loves him. So it is the "stop this ceremony" moment, a fight, the dragon (who fell in love with the donkey) to the rescue and the true love's kiss seals the deal and reveals the secret ...
Still with me? Despite a 19:00 start time some of the younger children did not make the second half as this is around 160 minutes (including interval) and that's a shame as the second half really has a lot of the fun in it. Part panto, part musical, part kids show this production rattles along but has a lot to get through - I can't help thinking that a few of the less entertaining songs (and perhaps a few set-piece scene changes) could be dropped in the interests of putting the story front and centre for children.
Having said that, this is a great show, plenty of laughs and film/show references for the adults and plenty of fart jokes for the kids (and the adults!) ... Go on, enjoy yourself - you know you want to!