I would not have any knowledge of biorhythms, nor would I care to have any knowledge if it were not for one library patron, an older gentleman that uses biorhythm information to know whether he should play the lottery.
(I cannot make this stuff up, its that strange.)
There are 2 websites I use for him to get his biorhythm. One of them has an interesting feature I will discuss momentarily.

Don't ask me to explain what a biorhythm is. I don't really know. I don't track myself to see when I'm having good or bad days, so I have no clue whether it works. I have found a certain comedic aspect to it.
Compatibility.

Now, if you go to www.facade.com/biorhythm/ and enter your birthday, you get this chart.
Along the right-hand side of the screen are the names of famous people that you can "check your compatibility" with. Or, if you like, there is a spot to enter a person's birthday.
Well, take a look at that list, and you'll see Natalie Portman is included.

For comic value online: How compatible are you?