But the late-night host, who ran afoul of the Palin family last year with a misfired joke, took it relatively easy on the young couple on Wednesday's "Late Show."
Letterman joked that Johnston will arrive for the wedding tied to "Sarah Palin's pickup." He also wisecracked that Bristol Palin made the announcement on an "hour-long ESPN special," a reference to the channel's show on LeBron James.
Letterman's final Palin joke poked fun at himself. Last year, he apologized to the Palins for a ribald joke involving one of their daughters. On Wednesday, the CBS host noted that Johnston, who made comments critical of the Palins, has issued a "heartfelt apology" to them.
Letterman paused a couple of beats, then said: "That kind of rings a bell."
