No famous encounters while backpacking, but several "encounters" while cycling. Twice, I accidentally rode through the middle of a "Walker Texas Ranger" set in a little town south of me. Chuck Norris and crew were displeased looking as I glanced back, wondering what the heck I'd just done.
Then, one beautiful sunset evening while on a training ride through Cedar Hill, Texas, I caught up with a line of maybe 10 classic cars going about 15mph. They were all 50's-60's vintage. As I was passing them, the drivers were waving me off, and I just waived back, smiling. At the front of the line there was a rigged out pickup truck with a Panaflex camera and and a guy yelling at me...and the rest of the cars. I had just ruined a sunset shot of "Born on the 4th of July" with Tom Cruise. (didn't see Tom) I messed up somebody's commercial shoot out there once, as well. Film crews used that part of Dallas often.