"Does this make any sense? You know what, I don't even know anymore. Here's all I ask. The highest valued stocks are now making the big moves — 'highest valued' meaning the highest price-to-earnings, highest price-to-sales [multiples] — so I'm begging you to do something for me: if you're going to own these stocks ... please know what you're buying," the "Mad Money" host said.
Cramer pointed to an indicator that could mean trouble for the seemingly unstoppable market. The S&P 500's proprietary oscillator, a measure that tracks how overbought the index is, just crossed 5, a high level that often indicates that a correction is imminent.
The most important thing for investors now is to know what they own and do their homework on the stocks in their portfolios regardless of how diversified they are, Cramer said.
"I am urging you to be careful," he said. "At this point, the odds do favor a pullback. It could give you a better chance to buy. Notice I'm not saying, 'Sell.' I'm just saying I want you to be ready."
With that in mind, Cramer turned to the stocks and events he'll keep a close eye on next week: