Earnings forecasts are odd beasts. Analysts feel that they have a good read on the companies that they follow. Through their own models and corporate guidance, they estimate how much a given company earned that quarter.

When a company misses that mark, it's often seen as a failure, especially if the consensus estimate was based on the company's own projections. However, when a company is doing so well that it blows past the Wall Street averages, investors should pay attention. There could be something exciting going on if even professional analysts have underestimated a company's prospects.

That said, let's take a closer look at a few of the companies that humbled the prognosticators last week.

We'll start with Apple Computer (NASDAQ:AAPL). It's getting to be a broken record with Apple, as the company -- yet again -- soared past Wall Street's targets. The hip computer and iPod maker earned $0.51 a share when the rest of the market was expecting $0.37 per share. Granted, some one-time tax benefits helped beef up Apple's bottom line, but the adjusted $0.38-per-share showing was still better than Wall Street was expecting and a whole lot better than the company's own initial guidance of $0.32 a share.

The stock dipped on the news. Perhaps investors have been spoiled by Apple's streak of recent market-thumping quarters. This toppling seemed merely mortal. However, the stock surged back the following day. Video iPod, anyone?

Winnebago (NYSE:WGO) was another topper. The RV specialist earned $0.46 per share in its final quarter of fiscal 2005. That was $0.04 ahead of the analyst consensus. Last month, Rich Smith proposed that results for Winnebago would come in strong over the next few quarters. The prediction was based more on the demand for readily available housing after yet another pesky hurricane season, but it seems as if Winnebago arrived early.

Then again, Winnebago and many of its peers, like Fleetwood (NYSE:FLE) and Coachmen (NYSE:COA), are trading lower than they were a year ago. Higher gasoline prices may have been a factor in dinging sales, but it should be noted that Winnebago still managed to grow its free cash flow over the past year.

Alcoa (NYSE:AA) is the third company that we'll be taking a closer look at this week. The company earned $0.33 a share for its most recent quarter. The analyst target for the aluminum giant was for $0.29 a share. Good deal? Not so fast. This is an important lesson in dissecting expectations. Just last month, Alcoa warned that its third-quarter numbers would likely come in between $0.27 and $0.31 per share. Yes, Alcoa went on to top that sum, but it was still well off the $0.43 per share that analysts were banking on before the company broke out the bad news.

So keep watching the companies that lap expectations. Over time, it will be a rewarding experience for investors. That's the kind of surprise that market watchers relish in the Rule Breakers newsletter service. The strategy has paid off as the average Rule Breaker selection has more than tripled the S&P 500's market return. Want in? Check out a 30-day trial subscription.

And come back next Monday to learn about more stocks that blew the market away!

Longtime Fool contributor Rick Munarriz is a fan of toppers, but he does not own shares in any of the companies mentioned in this story. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.