It's pretty much always infeasible to enumerate that space, but generally speaking there are a looooot of things that could qualify as special-looking enough to be included. All forms of english, foreign languages, language abbreviations, leet-speak, slang, pop-culture-inspired references, etc.
The odds of randomly tripping across something "special" eventually are pretty good. And bonus points if eventually one of those special coincidences is vaguely time-correlated with a real-world version of itself (eg, the number happens to be in the news, the slang word was recently used by a celebrity, etc).