Before last night's game, no known pair of teammates with a combined HBP total of 387 have been plunked in the same game. Jeff Bagwell and Craig Biggio got hit by pitches on August 6, 2004, giving Biggio 254 and Bagwell 126, for a total of 380. The only pair that could possibly have put up a better total is Bill Dahlen and Hughie Jennings for the 1903 Brooklyn Superbas (Dodgers). Jennings got hit once that year - his 287th, and Dahlen got his 104th and 105th that year. It's unlikely that they would have done it in the same game, but Retrosheet doesn't have game logs for that year so we can't prove it didn't happen.
So, Kendall getting his 251st plunk and Guillen getting his 136th is some kind of hard to explain record. Probably.