NEW YORK — David Letterman approached a sensitive subject Wednesday night when he got around to discussing Bristol Palin's engagement to Levi Johnston.

"He'll be arriving at the church tied to Sarah Palin's pickup," Letterman joked about Johnston during his Late Show monologue.

The host also quipped that Bristol announced the engagement news on an hour-long ESPN special, a reference to LeBron James sharing his plans to join the Miami Heat last week.

Letterman then poked fun at himself when he said Johnston recently offered a "heartfelt apology" to the Palin family. After a pause, the host remarked: "That kind of rings a bell."

The 63-year-old comedian famously caught heat last summer when he joked about one of the Palin daughters getting "knocked up by Alex Rodriguez."

Prior to launching into his Palin bit, Letterman spent plenty of time mocking Mel Gibson.

"His rage today was so volcanic they grounded flights in Europe," joked Letterman.