Ironically, James Kyson Lee has spent most of three seasons on Heroes acting opposite one man -- this in an overcrowded series with arguably more super-powered characters than all the X-Men movies combined.

That one man would be Masi Oka, who plays the time-bending Hiro Nakamura, and to whom Lee's character, Ando Masahashi, has acted as exasperated-but-faithful sidekick since episode one.

Do they ever get sick of each other?

"Every day," Lee says with a laugh over the phone from L.A., where he's between scenes filming Season 4.

"Actually, we're fine. We're like brothers in a way," says the actor, who is a featured guest this weekend at the massive genre fest Fan Expo Canada at the Metro Toronto Convention Centre. "I like to think of Hiro and Ando like Tom Sawyer and Huck Finn -- how they get each other into trouble and are always saving each other's butts. It's been a fun ride."

Starring in one of the few U.S. network shows with international appeal, the Korean-born, New York-raised Lee and other castmembers have toured the world promoting the series. "It's quite fascinating when you see yourself dubbed in Spanish or French or German."

But the real acid test was Japan. Hiro and Ando spend most of their time speaking to each other in subtitled Japanese -- a language Oka speaks fluently, but which Lee initially didn't speak at all (in the context of the show, Hiro spoke virtually no English at first, and Ando often acted as his interpreter).

But Lee took his Japanese seriously.

"I insisted on learning everything I say, all the vocabulary, all the grammar. I've had a coach since the beginning and I feel more comfortable every season.

"In Japan they dub everybody in Japanese, but a lot of people watch the show in its American version, and they know my family is from Korea. In the beginning, it was obvious to them I was still working on the language. They've noticed I'm getting better."

Despite playing second banana to Hiro, Lee started noticing a sizable presence of Ando fans almost immediately.

"I get called Ando on the street a lot, which always makes me do a double-take. I feel like he's always been a character people latched on to, maybe because he started out as a human being in the show, without powers.

"And a lot of people felt like he represented them. Now, of course, he's got a power of shooting lasers -- what we call the 'Ando Blast' or the 'Crimson Arc.' It's icing on the cake for me."

At season's end, the flying politician Nathan Petrelli (Adrian Pasdar) had been killed by the serial-killer Sylar (Zachary Quinto), who was then mind-controlled by Matt Parkman (Greg Grunberg) into shape-shifting into Nathan's form and living his life as if nothing had happened, effectively making Sylar the one who died. (Got that?)

"We (Hiro and Ando) were there actually also when we burned Sylar's/Nathan's body. This season four (which debuts Sept. 21 as a two-hour premiere on NBC/Global) we start off in Japan.

"Ando is starting a new business with Hiro, which will thrust us into really unusual adventures. Also, Ando this season is going to be interlinked with somebody very unexpected, which is going to be a nice surprise for the audience."

In response to critics' and audience complaints that the show had become too complicated, Lee says, "The format this season is we're focusing on fewer characters per episode, and giving them deeper storylines. Maybe five stories per episode. You're not trying to track down 10 or 12 storylines in one episode anymore.

"I think that (over-complication) became a real issue, and we're kind of going back to what made the show take off in the first season. There were few enough stories then that we were able to somehow tie everything together every episode."

But Heroes will inevitably run out of steam, he says.

"Every show is going to have an end, and a show like ours obviously can't go on forever or it will get diluted. But I feel we have a few good years left."