Lacy appeared in the World Series three times for the Dodgers in 1974, 1977, and 1978. He appeared in the 1979 World Series as a member of the Pirates.
On May 17, 1978, Lacy hit his third consecutive pinch-hit home run, setting a major league record, as the Dodgers beat the Pirates 10–1. His previous blasts were on May 2 and 6th. Lacy's record was matched in 1979 by Del Unser, who hit three consecutive pinch-hit home runs on the 30th of June, 5th and 10 July.
In 1985, Lacy was among a number of players caught up in the Pittsburgh drug trials scandal. In 1986, he was given a 60-day suspension but was allowed to continue playing if he donated five percent of his base salary and contributed 50 hours of drug-related community service.