CNBC's Jim Cramer warned the market could be due for a pullback after a hot run in 2019. The "Mad Money" host also doubled down on his newfound bullishness for Tesla and argued that the electric carmaker's market value could be worth double what it is now.

CNBC's Jim Cramer on Tuesday warned investors that stock prices could be on a downward trend over a short period of time.

"I want to buy these stocks, but only into weakness. However, keep in mind that we've run a great deal, so you have to be prepared for an exogenous event that causes a pullback that will give you opportunities to buy at lower, less-expensive levels," the "Mad Money" host said.

's market cap is nearly the sum of and .

Cramer said he's "dumbfounded" that the electric carmaker isn't even higher, saying it could be double that of the traditional automakers.

"Because the stock market loves growth and this market, in particular, can't get enough of it," the host said. "Tesla has growth in spades; of course investors will pay up for it. GM has barely any growth. Ford's actually shrinking. Nobody wants to pay up for stagnation."

In Cramer's lightning round, the "Mad Money" host made buy and sell calls on viewers' favorite stock picks.

: "American Tower is trading right now on what the judge is going to do on the merger between T-Mobile and Sprint. I say wait a few days, the stock's coming down and then you'd get a better chance to buy."

: "I think ... this thing can go to $17, $18 without a problem. They have fixed the company. I am a believer in Mattel."