This film was a real disappointment. It had a good premise and a good cast but, apart from one or two amusing set-pieces, mainly failed to deliver.
The plot partly relied upon mistaken identity due to the main character having changed his name. His real name was Gaylord Foker (oh my aching ribs!). The name was unnecessarily vulgar bearing in mind that it's main task was to set up the confusion of identity scenario (and hey, I liked the dialogue in Goodfellas and Casino so its not a sensibility issue). The name was used at intervals throughout the film to get cheap laughs in a way that was more suited to the "Carry on" films. It wouldn't be worth mentioning, except that so many scenes in the film seemed to rely on it for laughs (even before his 1st name was revealed to be "Gaylord").
Although one or two of the set-pieces were funny, every single one of them was telegraphed way ahead. De Niro gets all emotional about his Mothers ashes - Greg breaks the urn, Greg floods the lawn with s**t - his girlfriends ex drives up in a truck and sprays them with it, the ex carves a beautiful altar for her sister's wedding - Greg burns it down. And so on and so on - you get the picture? All we were missing was Greg leaving a rake for someone to step on and wack themselves in the eye
Imagine a comedy that combines the intelligence and sophistication of "Frasier" or the "Phil Silvers Show" with the slapstick of the Marx Brothers - well you ain't imagining this film. Mixing slapstick/farce with a bit of sophistication is fine when done well ("The Producers" for example) but here the comedy never got sophisticated enough to provide a counterpoint to the -adequate- slapstick. The only low gag they missed was not having the Thai honeymoon destination being Phuket!
This was a film that intermittently promised to develop into something good (De Niro's poem to his dead mother for instance), and the cast did their best with thin material. In the end though it couldn't build on it's few bright spots - it could have been much, much better with a bit more effort.