Well, he's a different Jim Carrey, anyway. Still playing crazy but in The Number 23, he isn't playing for laughs. His character, Walter, is gradually losing his mind thanks to an anonymously written novel his wife buys for him as a birthday gift.
As Walter reads his gift, he moves from indifference to mild interest, then to obsession and paranoia bordering on suicidal-homicidal tendencies. It's tense wondering what might send him over the edge. Walter's a bit like Carrey's other character, the Cable Guy, but with a deeper exploration into his psychosis and motivations.
The novel he reads seems to parallel his life and he comes to "realize" that the number 23 rules his life like a family curse. Applying numerology on the minutiae of his life -- e.g., name, birthday, address, memorable events -- somehow they all add up to 23, just like it does for the novel's protagonist.
As the gristly details of various characters' deaths in the novel come to light, Walter becomes convinced that they refer to real events, and that he is about to become the anonymous novellist's next victim.
For some people, literacy and mathematics are not a good thing.
Anyway, this whole numerology nonsense is all about finding things just because people start looking for them. We creep ourselves out observing the staggering coincidences between the assasinations of presidents Lincoln and Kennedy, for example. But if you think about it, the probability of the digits 2 and 3 appearing together at any time is as high as any other pair of numbers appearing together: only 1 in 89, if I calculate correctly. And when we accept multiples of the 2 digits, plus the reverse order of the digits, the odds shrink significantly lower still. 23 could rule your life as well! Coincidence? I think not!