San Francisco is filled with interesting places -- rowdy bars, relaxing parks, and sites that are simply a pleasure to look at. But the city is also blessed with actual human beings who count as must-see attractions in and of themselves. Below, a handy guide to three of our favorites:

Real Name: Frank Chu.

What Everybody Calls Him: That Guy, You Know, With the Sign.

Dossier: Back when Monicagate started, so did Frank Chu, wandering around downtown hoisting a sign reading "IMPEACH CLINTON." Fine. Then he started hoisting a sign saying "IMPEACH CLINTON BUSH REAGAN NIXON," and you kind of wanted to point out that the Nixon thing was, you know, already taken care of, in a way. Then it was "IMPEACH CLINTON 12 GALAXIES GUILTIED TO A ZEGTRONIC ROCKET SOCIETY," and you got a little scared. But Chu is still there, changing the signs weekly and protesting something on a cosmic level. He's a decidedly loopy part of the landscape, but we're glad he's around.

Viewing Opportunities: Market Street near the Embarcadero around the late-afternoon and evening rush hour; spies have recently found him in Berkeley's Sproul Plaza too.

Real Names: Vivian A. and Marion B. Brown.

What Everybody Calls Them: Those Twins, You Know, Always Dressing the Same.

Dossier: The Brown sisters moved to San Francisco from Los Angeles in 1969 and have routinely become the models of choice for "friends fly free" ads and any other advertisements where adorable twins wearing matching mink coats seem appropriate. Charming and approachable, they're usually happy to have their picture taken. They really ought to strike you as thoroughly creepy, but they're somehow not.

Viewing Opportunities: Evenings are best. Try the nether reaches of Nob Hill (say, Sutter Street near Powell) or Cala Foods on California and Hyde (where they can sometimes be found shopping).

Real Name: David Johnson.

What Everybody Calls Him: Jesus Christ, You Scared the Crap Out of Me!

Dossier: For years panhandler David Johnson has worked as the "Bush Man" at Fisherman's Wharf, hiding behind a bunch of twigs and scaring the bejeezus out of people as they walk by. It's a shtick, sure, but it's one we admire. After all, Johnson's working for the money, exploiting the fact that unsettled people are people willing to give away some cash. Plus, every time we see a family visiting from Omaha fly 10 feet into the air, we're pleasantly reminded that San Francisco is a brand-new thing to a lot of folks; watching the Bush Man at work is seeing the city with new eyes.

Viewing Opportunities: Throughout Fisherman's Wharf, usually close to Pier 39. All day.