There's something most investors have in common with their game-changing winners: They got in early. That doesn't mean you have to find the next Microsoft or Apple as they go public, but you do have to be diligent about finding stocks with long-term upside early in the game. Here are two stocks that fit the bill and might be investments investors can't afford to overlook. 

Feed them like family

Whether younger people are increasingly opting for pets and delaying parenthood or older generations are filling a quiet household with a new furry friend, Americans are clearly devoting more time and money to their animal companions. At the same time, there's been a focus on healthier eating, and that trend appears to be trickling down to our pets as well.

That's great news for Blue Buffalo Pet Products (NASDAQ:BUFF), the fastest-growing major pet-food company in the U.S., with a focus on high-quality and natural ingredients. The company has quickly grown its Blue Buffalo pet food into a billion-dollar brand based on sales and owns roughly 6% share of the overall pet-food industry.

Owning shares of Blue Buffalo comes with a couple of advantages, even though it's part of a highly competitive industry. First, with the company's focus on premium ingredients and its expansion into therapeutic foods -- which are more regulated and require veterinarian prescriptions -- its research-and-development team has a slight edge. These foods have a different shelf life, because of the difference in ingredients, and Blue Buffalo's team has developed that knowledge.

Also, once pet owners are on a more premium or prescription food, they tend not to change course even if the economy takes a downturn. And the company's products have some switching costs, as changing pets from one food to another does take a little extra effort, assuming owners follow recommendations of a gradual shift.

Blue Buffalo is coming off a strong first quarter that beat estimates. Its net sales were up nearly 8%, and its net income up 18.1%, over the prior year. If management can continue to expand its therapeutic-food offerings, thus building its brand image as a premium pet-food manufacturer, and methodically expand internationally, it should help fuel the company's overall growth story for years to come.

Car buying done right?

While we all love the smell of a new or used car as we drive it off the dealership parking lot, we're probably all in agreement that getting to that point is far from enjoyable. Has anybody ever enjoyed the car-buying process, or do we all want to drive away from the experience as quickly as possible? That's where Carvana Co. (NYSE:CVNA) comes in, smelling opportunity: 

Graphic showing size of car industry ($1.1 trillion)

Image source: Introduction to Carvana's May 2017 presentation.

The company is offering a unique car-buying experience, one that seems aimed at millennials. One look at the vending-machine concept, and you can easily imagine a younger consumer taking selfies during the car purchase. Scoff at that idea if you want, but it's certainly unique and shareable, compared with the status quo at most dealerships -- and Carvana gets to enjoy free word-of-mouth advertising.

Carvana's multi-story vending machine car buying concept.

Image source: Carvana. 

Carvana has just reported its first quarter as a public company, so the story has a long way to go. But what investors should consider is that the management team has already nailed a repeatable market-entry playbook. It has a team of expansion advocates with defined market-launch capital expenditures, a logistics network, and a turn-on marketing program. That's helped Carvana's total number of operating markets jump from three in 2014 to nine a year later and 21 in 2016.

One quarter doesn't make a trend, but its first-quarter results are promising. Retail units sold were up 120%, to 8,334, and revenue jumped a similar 118% to $159.1 million. The company remains unprofitable, but there is immense room to improve its operations. The focus going forward will be to increase the number of markets it participates in to sell incremental vehicles, reduce the average days to sell a vehicle, increase the conversion rates of its marketing, and develop new products and services to generate other streams of top-line growth.

Teresa Kersten is an employee of LinkedIn and is a member of The Motley Fool's board of directors. LinkedIn is owned by Microsoft. Daniel Miller has no position in any stocks mentioned. The Motley Fool owns shares of and recommends Apple. The Motley Fool has a disclosure policy.