Shout-out to my wife. After all of the double-plays tonight she started telling me about being at an Astros game when she was a girl where they turned some ridiculous record-setting number of double-plays. We looked things up, and sure enough, on May 4, 1969, against the Giants, they turned 7 double-plays in 9 innings, with the immortal Curt Blefary involved in all of them.
We also discovered that the Astros hit two grand slams in the same inning (the 9th inning, no less) against the Mets on July 30, 1969.