Cramer: This 'cannabis' stock will quickly double

Cramer's favorite marijuana stock

Jim Cramer strongly endorsed an analyst's bullish call on GW Pharma (GWPH) in his "Stop Trading" segment on CNBC's "Squawk on the Street" today.

The UK-based company is working on prescription medicines based on cannabis to treat a number of medical conditions.

Its stock soared as much as 43 percent to $65.97 after Morgan Stanley started coverage of the stock with an "overweight" rating and a price target of $103.

Cramer called Morgan's recommendation "timely" and "bold," predicting the stock will quickly reach the target.

"It's not a medical marijuana stock. They have a novel platform. It is an epilepsy company."

Cramer warned investors to stay away from other marijuana-related penny stocks. "Forget it! If you like cannabis, and I'm not necessarily speaking about 'liking' cannabis, it's GW Pharma."

—By CNBC's Alex Crippen. Follow him on Twitter @alexcrippen.