CNBC's Jim Cramer on Monday reviewed the prospects of the newest additions to the S&P 500: AppLovin, Robinhood and EMCOR Group.

"Of the three newest members of the S&P 500, AppLovin and Robinhood are both red-hot stocks that've gotten even hotter — I expect them to move higher over time, but they might pull back now that they've gotten a boost," he said. "But EMCOR, this one's got a lot less hype, and I got to tell you, it's got a very attractive story, which makes it a buy right now."

S&P Global announced last Friday that the three companies would join the index on September 22. By Monday's close, advertising technology company AppLovin was up 11.59%, trading platform Robinhood added 15.83% and infrastructure outfit EMCOR Group inched down 0.61%. While the changes don't begin just yet, Cramer suggested buyers take action as soon as they hear such an announcement.

AppLovin started out as a platform to help mobile video game developers partner with advertisers, but it has since become a more major player in the digital advertising space. The stock has traded unevenly since it came public in 2021, Cramer said, but it has seen immense gains recently — and revenue has nearly doubled over the past three years. Despite the stock's "crazy" action, Cramer said he has never been able to fully turn against the company because of its impressive growth. He also said he has faith in the company's management because AppLovin has been able to expand its reach in the industry fairly quickly. Many AppLovin investors have been expecting the company to join the S&P 500, he continued, indicating that he expects some profit taking as a result. He suggested waiting for weakness to buy shares.

To Cramer, Robinhood has "reinvented the retail stock brokerage business," and the stock has been a "juggernaut" over the past few years. He said he's been impressed with its ability to expand business into new avenues — such as options and cryptocurrency trading, as well as retirement accounts and credit cards. Cramer said he's also bullish on Robinhood because baby boomers are starting to transfer wealth to younger generations, who might be more likely to invest using the company rather than more traditional avenues like Fidelity or Charles Schwab. Like AppLovin, Cramer said he expects some selling and advised investors to buy on weakness.

EMCOR Group is "perfectly on theme for the current moment," Cramer said, because much of the engineering and construction contractor's business relates to industrial and energy infrastructure. To Cramer, EMCOR Group has been able to maintain solid growth because of the data center boom. He said analysts expect the company to continue to perform in part because of the reshoring of semiconductor and pharmaceutical plants spurred by the Trump administration's tariffs. Cramer said it could be worthwhile to buy the stock at its current levels.

"There is nothing more positive for your stock than joining the number one large-cap benchmark," he said. "So many index funds exist to mirror the S&P 500, meaning they'll all be forced to buy the new additions."

Robinhood directed CNBC to a recent statement from CFO Jason Warnick.

"We are thrilled to be recognized by S&P Global as a new member of the S&P 500," he said. "We remain focused on our mission to democratize finance for all - we've made great progress and there's much more to do."

AppLovin and EMCOR Group did not immediately respond to request for comment.

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