On paper, the inspirational drama The Pursuit of Happyness has all the ingredients for a disastrous ego trip. Based on a true story, the film casts Hollywood megastar Will Smith as Chris Gardner, a single father who went through a period of homelessness in the early '80s after switching careers from medical-supply salesman to stockbroker. To play this ordinary guy, Smith added some grey to his hair and grew a silly-looking mustache in an effort to make the audience forget his marquee-idol good looks (and, no doubt, to send a signal to the Academy that he was ready for another Oscar nod). That's strike one. Strike two is the fact that Smith's own son Jaden was cast as Gardner's five-year-old boy Christopher, who sleeps alongside his father in various shelters and even a public restroom during their time on the streets. While nepotistic casting has occasionally yielded positive results--think of Ryan and Tatum O'Neal in Paper Moon--most of the time the outcome is closer to Sylvester and Sage Stallone in Rocky V. Strike three comes in the form of the film's mawkish trailer, which begins with one of those generic trailer voices intoning lines like "Chris Gardner was doing his best, but his best wasn't enough" and closes with Christina Aguilera wailing about "spreading your wings" while Smith's face cycles through various degrees of sadness. It's all so aggressively sentimental, you almost feel as if the filmmakers are sitting in the theatre next to you threatening you to cry or else.

Fortunately, the finished film doesn't attempt to hold your emotions hostage in such a belligerent fashion. That's not to say that The Pursuit of Happyness isn't out to make the audience weep. It most certainly is and the movie is at its weakest whenever it reaches out to tug a little too hard on the ol' heartstrings. What ultimately keeps Happyness on track is Will Smith's perfectly pitched performance. Few contemporary movie stars are as innately charming as Smith and he uses that charm to great effect here, getting the audience on Gardner's side right away and keeping us there even when the film itself loses momentum. Smith has proven himself capable of tackling more challenging material in the past--Ali and Six Degrees of Separation come immediately to mind--but this is arguably his first real adult role. Throughout the film, Gardner is confronted by problems that can't be solved by stepping into a boxing ring or shooting a bunch of aliens. Unable to play his usual man of action, Smith has to find other ways of dealing with these conflicts. There's a scene early on in Happyness where Gardner shows up for an interview at the prestigious brokerage firm Dean Witter in the hopes of being chosen for their internship program. As if that's not already demanding enough, he spent the previous night in prison because of unpaid parking tickets and has arrived at the office clad in the paint-spattered jumpsuit he was wearing when he was arrested. Now Gardner has to depend entirely on his wit and his words in order to make the heads of the program look past his appearance. And damned if Smith doesn't sell this unlikely scenario completely.

If you wanted further proof that The Pursuit of Happyness is really The Will Smith Show, you need only look at the lackluster performances from the supporting cast. The usually reliable Thandie Newton is twitchy and mannered as Gardner's unhappy wife, who eventually abandons her family to go live in New York, and all of the faces the stockbroker-in-training encounters at Dean Witter are interchangeable. As for Jaden Smith, he's relaxed and comfortable when horsing around with Dad, but his line readings in the more emotionally demanding scenes fall flat. At the same time, his presence was probably a huge boon for his father, as it gave him a familiar face to play off rather than having to forge a bond with a professional child actor. When Smith gazes at Jaden, the love in his eyes goes beyond acting--he's living in the moment with his son. And those are the scenes where even the most hardhearted viewers might find themselves wiping away a tear.