×

The TV show that makes a stock market drop

Adam Cheng in "The Greed of Man"
Source: TVB
Adam Cheng in "The Greed of Man"

When this Hong Kong actor appears on the silver screen, watch out for a possible selloff in the Hang Seng.

The index's recent rally to seven-year highs could abruptly pull back on Tuesday after the television drama "The Greed of Man" from the local TVB network reairs in Hong Kong at 12:15 a.m. local time (12:15 p.m. Monday ET).

First aired in 1992, the show stars Adam Cheng in the role of "Ting Hai." The character is a stock market speculator who put a negative face on the financial world with his triad involvement.

The local stock market promptly plunged 20 percent over the following few weeks, kicking off a phenomenon called the "Adam Cheng effect" or "Ting Hai effect."

In the two decades since, nearly every time the 68-year-old Cheng has appeared in a movie or television show—which has been more than 30 times—the Hang Seng declined.

Most recently in 2013, the index fell nearly 3 percent in the week after the premiere of his movie "Saving General Yang." Even with the April 13 announcement of the reshowing of "The Greed of Man" there was a 1.6 percent decline in the index the next day.

Read MoreShares hit by China trading clampdown fears

The Hang Seng and the Shanghai composite have recently rallied to seven-year highs, driven mostly by hopes for government stimulus to combat slowing economic growth.

"There are things going on that defy logic," Lance Roberts, general partner at STA Wealth Management, said of the recent rise in Asian stocks. "The Chinese have a gambling mentality anyway. This plays into the whole mentality they have about risk-taking."

Chinese futures sold off in after-hours trading Friday on news of coming government regulations to expand short selling and limit over-the-counter margin trading.

"China is a market that is idiosyncratic," John Canally, investment strategist and economist at LPL Financial, said of the futures' decline on Friday. "At any given time you could get a ... dose of good news or bad news and those tend to even out."

Representatives of Citi and Standard Chartered in Hong Kong said they did not take the "Adam Cheng effect" seriously. CLSA research reports on the phenomenon have not found a logical cause for the effect.

The actor said that if the effect was really true, he would have generated a fortune already, and financial professionals could have retired already, according to a report by the mainland Chinese paper People's Daily.

For example, the article noted that Cheng's appearance in Hong Kong television dramas in 2005 and 2006 did not cause a selloff in the Hang Seng.

If there is any rational explanation, it would be that the actor's reappearance is a reminder of how volatile and crazy speculation in the stock market can be. Besides the dramatic presentation of the global 1973 stock market crash, the drama's self-appointed stock market "god" tells Cheng's rival Fong Chin-bok the key to winning in the stock market is "to leave early."

Read MoreHow a Chinese travel rule spooked luxury investors

Whether or not that advice is solid, Fong wins out in the end.

Benjamin Graham, the late American investing sage, would remind us that there are fundamental differences between investors and speculators. "The investor's chief problem—and even his worst enemy—is likely to be himself," he once said.