Tesla stock jumps on model "D" tease

Tesla Motors (TSLA) stock is up more than 4 percent this morning. The catalyst was a tweet by CEO Elon Musk Wednesday evening about a product announcement scheduled for October 9.

The tweet read, "About time to unveil the D and something else".

And then Musk complicated the picture even more with another tweet a few hours later. It read: "I love the Internet. Comments had me literally ROFL. No, it wasn't intentional. Glad I didn't mention the other letter!" But it seems unlikely that the D reference was a mistake, as Musk had originally included a picture of a rising garage door with the letter D on it and the front end of a vehicle peeking out from underneath.

No one outside the company is sure what the D, let alone the something else, would be or what might be announced next week. There are several possibilities.

One is that the D might represent a less expensive electric crossover -- a cross between an SUV and a passenger vehicle. Tesla has already announced its Model X crossover, which will have a low center of gravity for better handling and 0 mph to 60 mph acceleration in 5 seconds. The X is expected to ship to customers in the fall of 2015. A more economical model could prove popular. Musk has already said that the company was working on a small crossover that would reach the public in "three to four years."

Another possibility would be a small sedan, also mentioned by Musk, which would run around $30,000, rather than the $70,000 for a Model S sedan.

A cheaper model would help the company broaden its customer base and, in doing so, help improve the scale of manufacturing that, in turn, could drive down the general cost of building its cars.

According to Global Equities Research analyst Trip Chowdhry, the other thing might be a display of how an iPhone could replace the key fob to remotely open or start a Tesla car.