John Candy gives one of his best performances as a good-natured, well-meaning, happy-go-lucky gambler on the verge of losing his girlfriend when he is put into a situation where he is completely out of his depth. But relying on much of his experience, some of it, shall we say, less than stellar, to best cope with his situation.
The comedy and visual gags abound throughout the movie and the interplay between his character and the three children he has been put in charge of is priceless. The best interactions are those between him and the eldest child Thea, who is going through many issues, teenage angst, mixed emotions dealing with boys, rebellion against her parents for uprooting the family into a new city and having to deal with and "clean up" after Uncle Buck's attempts at doing the best he can to manage the family.
The story can be summarized as a growing up and maturing process for both Buck and Thea, who at the beginning of the movie almost completely despise each other. As the film progresses, both characters build off each other and come to some very interesting realizations that life isn't all that bad.