Biggio makes the world go plunk.
In the seasons from 1988 to 2005, Craig Biggio was hit by a pitch 273 times on 253 days. On those days when he got hit, 2,496 total plunks were recorded in the majors, with Biggio accounting for 10.9% of them. On days when Biggio didn't get hit during those seasons, there were an average 7.57 plunks per day, while on days when Biggio recorded a plunk there were 9.87 plunks per day. That may look as though Biggio drags up the average on days when he gets plunked, but that's not the whole story (since he doesn't average 2.3 plunks on days when he is plunked). Excluding Biggio's HBPs, there have been an average of 8.78 other HBPs recorded on days when Biggio was hit. On days when Biggio was hit once the rest of the league averaged 8.70 plunks, and on days when he was hit twice, the rest of the league was hit 9.75 times per day. Excluding other batters that the pitcher who plunked Biggio hit that day, the averages move down to 8.56 on 1 plunk days for Biggio, and 9.60 on 2 plunk days, so it doesn't appear that the league-wide increase in plunks on days when Biggio is hit is just caused by 1 pitcher hitting a lot of people, including Biggio. Either there are certain days when lots of batters get hit, and Biggio is the beneficiary (sort of) of that, OR, on days when Craig Biggio gets hit, the rest of the league somehow follow his example. Excluding the Astros games entirely, the averages are 7.04 plunks on days Biggio doesn't get hit, 8.06 plunks when he gets hit once, and 9.1 HBPs on days he gets hit twice. So, if he's inspiring more batters to be hit, it goes much further than the rest of his team, and their opponents.
The highest total of HBPs recorded league wide on a day when Biggio was hit by a pitch is 22, on June 1, 2004. There have been only 2 other days in the 1988 through 2005 seasons with as many plunks recorded - August 22, 2004 (on which Biggio played but was not plunked) and July 20, 2002 (on which Biggio did not play). July 20, 2002 had a 16 game schedule, but the other two 22 plunk days where 15 games. On June 1, 2004, Biggio was hit by Glendon Rusch, and in the same game Brad Lidge hit Todd Hollandsworth. Also on the day, Bronson Arroyo hit Raul Mondesi and Adam Kennedy twice, Casey Kotchman was hit by Allen Embree, Jason Varitek was hit by Bartolo Colon, Jody Gerut was hit by Ryan Drese, Jaque Jones was hit by John Halama, Sidney Ponson hit Tony Clark, Eric Chavez was hit by Damaso Marte, Dustin Hermanson hit Shea Hillenbrand, Steve Sparks hit AJ Pierzynski, Mike Koplove hit Barry Bonds, Brad Penny hit Jason Larue, Jeff Weaver plunked Scott Podsednik and Geoff Jenkins, Shawn Green was hit by Doug Davis, Kevin Millwood hit Jason Phillips, Scott Rolen was hit by Ryan Vogelsong, Jeff Suppan hit Daryle Ward, and Aaron Cook plunked Mark Loretta.
June 8, 2000 is the only day on which Craig Biggio was the only batter in the Majors to record a plunk. There were only 3 games played that day. In terms of plate appearances per plunk, the day on which Biggio was plunked that featured the fewest HBPs was July 25, 1997. Only one other batters was hit that day in 15 games, for a rate of 1 HBP per 560.5 plate appearances. On the 22 plunk day of June 1, 2004, a batter was hit, on average, every 57 plate appearances.
In other vaguely related news, on Saturday, Red Sox center fielder Coco Crisp became the 10th player in recorded history to reach 2000 major league plate appearances without getting hit by a pitch. Of the 9 others to reach that mark, only 4 of them eventually recorded a plunk. The other 9 are Mark Lemke, John Kruk, Herm Winningham, UL Washington, Bill Bergen, Mickey Witek, Chipper Jones, and Mickey Mantle. (This list excludes people who had plate appearances before plunks were recorded)