Slow and steady typically wins the race in investing. Being the tortoise and not the hare by having a long-term outlook is how investing legends like Buffett and Lynch became, well, legendary.

Yet sometimes you can win handsomely when a stock takes off like a rocket in a short period of time, turns on the afterburners, and soars to new heights. While Dynegy (NYSE: DYN), (NASDAQ:OSTK), and Skechers (NYSE:SKX) each jumped 20% or more in a week's time or less, investors probably weren't betting that would happen.

Even though that underscores the buy-and-hold mantra of the investing greats, let's look at why each stock did spike and whether the moves are sustainable.

Petrochemical plant

Image source: Getty Images.

Dynegy (up 21%)

There's nothing like a possible merger to send a stock higher, and Dynegy benefited from reports it was in advanced talks with Vistra Energy (NYSE:VST) to get bought out. That sent Dynegy's stock soaring from $9.21 a share to $11.18 in only two days.

It announced yesterday the merger was in fact going to be completed. Dynegy shareholders will receive 0.652 shares of Vistra Energy for each share of stock they own, and when completed, Vistra shareholders will own 79% of the company and Dynegy shareholders will own 21%.  Dynegy's stock rose an additional 6% on the news.

There had been rumors of a deal in the works since the spring. The energy industry is undergoing consolidation, yet it has also been plagued by bankruptcy. Dynegy went bankrupt in 2011, and Vistra got spun off out of the bankruptcy of Energy Future Holdings. The combined companies, though, could be a powerful combination, though Dynegy brings with it an excess of debt.

Ethereum token 3D rendering

Image source: Getty Images. (up 32%)

I'll be the first to admit I don't understand the concept of cryptocurrencies as a valid alternative to fiat money, but the growing acceptance among investors, users, and, arguably more importantly, businesses means what was once a fringe system is on the cusp of becoming mainstream.'s stock hasn't been moving higher as a result of its retail prowess, but rather because of its investments in cryptocurrency. While it recently announced it would accept Ethereum, which is similar to the better-known bitcoin, what really sent Overstock's stock soaring was the news it was going to have an ICO, or initial coin offering, which, like an IPO, allows companies to raise money, except they do it by selling their own virtual coins to be used on cryptocurrency blockchains.

Overstock's shares are up almost 60% over the past month, after the company announced it would create an exchange to trade cryptocurrencies. Now it's creating its own token or coin to use, and the market, which has grown increasingly excited by the technolog, has sent shares soaring.

Basketball player dunking basketball

Image source: Getty Images.

Skechers (up 36%)

Sneaker maker Skechers had been performing as if someone tied its laces together, but it reported third-quarter results that beat not only analyst expectations but its own as well. It reported nearly $1.1 billion in sales, a 16% increase from last year, but also well ahead of Wall Street's forecast of $1.07 billion and surpassing management's guidance of $1.075 billion.

It reported growth here at home and overseas, and though domestic sales growth of 1.4% was modest, international sales were nearly 26%, with China alone 50% higher.

What caused the report to catch everyone by surprise is just how well it was doing compared with how hard other sneaker makers are having it. While Adidas (OTC:ADDYY) has done well for itself, both industry leader Nike (NYSE:NKE) and Under Armour are stumbling badly.

Skechers still has a long way to go to catch up to Nike, which still holds a commanding 35% share of the market (Adidas is second at 11%), but now that it's hit the ground running, it has a better shot at accomplishing that goal than when it was stumbling over its own feet.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.