Before watching number three in the Shrek franchise, forget the clever subversion of fairytale constructs, the subtle and well-chosen cultural references, the jokes that actually make you laugh rather than question why on earth they had been included (basically everything that the first Shrek film was about and that Shrek 2, whilst not quite as successful, managed to at least remain faithful to), because Shrek The Third contains none of this. The plot is a rehash of elements from the first two films, feeling entirely uninspired and never generating much interest. Shrek's character arc, focused on whether he's ready to become a father, feels heavy-handed and comes and goes too much to ever feel properly developed. The connected moral message of facing up to responsibilities feels muddled and is concluded in a wholly unsatisfactory manner.
The returning characters feel tired or unnecessary, and choosing Prince Charming (Rupert Everett) as the primary antagonist here when he was introduced as second fiddle (and a bit of a tit) in the first sequel is setting up to fail from the very start. Mike Myers and Cameron Diaz as Shrek and Fiona respectively never offer more than going through the motions. Donkey (Eddie Murphy) and Puss In Boots (Antonio Banderas) are entirely wasted here, with a half-baked body switch "twist" thrown in late on in proceedings which goes nowhere, as if the writers suddenly realised they'd wasted two of the franchise's strongest assets. The new characters are no better: Arthur "Artie" Pendragon is underdeveloped and irritating, with Justin Timberlake's vocal performance never fitting the character; Merlin (Eric Idle) is even worse - a pathetic "new age" wizard whose every joke falls flat.
Shrek The Third is one of the laziest pieces of cinema I've ever experienced. Every aspect of it smacks of apathy on the part of everyone involved, from the stars to the director to the animators. It lacks energy, imagination and humour and represents the very lowest end of computer-animated cinema. Until Dreamworks is no longer happy to churn out dross such as this, it will never truly be able to compete with Pixar.