What happened Shares of Clean Energy Fuels (NASDAQ: CLNE) dropped as much as 20% in trading on Thursday after a big shareholder revealed a sale of stock. Shares of the energy stock are down 15.2% at 3:20 p.m. EDT. So what Total Marketing Services, which now holds 26.7% of Clean Energy Fuels' outstanding shares, revealed that it sold 1.25 million shares earlier this week. Total Marketing Services has been selling shares for a few weeks, so the sale isn't entirely surprising, but when large shareholders sell a stock it can be seen as either a lack of confidence in the company or a view that shares are overvalued by investors. Image source: Getty Images. In addition to this share sale, Clean Energy Fuels itself sold 10.5 million shares on June 8, for proceeds of $100 million and has now sold 22.8 million shares and raised $200 million since the May 10 at-the-market equity offering program was announced. If the company itself is taking advantage of the higher stock price this week investors may have been too optimistic in pushing shares higher. Now what Earlier this week, Clean Energy Fuels seemed poised to become the next meme stock on Reddit, but those hopes may have been dashed today. Insiders and Clean Energy Fuels itself are quickly unloading shares after the rise in the stock price and traders are taking notice. Meme stocks can rise quickly and fall just as fast and investors are seeing the downside of the meme trend today. 10 stocks we like better than Clean Energy FuelsWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and Clean Energy Fuels wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of June 7, 2021 Travis Hoium has no position in any of the stocks mentioned. The Motley Fool recommends Clean Energy Fuels. The Motley Fool has a disclosure policy.Source