Lukaku scored a brace on his Premier League debut for United on Sunday afternoon, with the Red Devils opening their 2017-18 campaign with a 4-0 victory at home to West Ham United.
Rashford also played a key role in the success, setting up Lukaku's first of the match, and the summer signing from Everton has revealed that the duo "clicked" as soon as he arrived at the club last month.
"With me and Marcus, there's something special," Lukaku told MUTV. "Hopefully we can produce even more [in the future] than we did today. We clicked from the first day that I arrived, and I knew that he would help me settle in at the club."
Next up for Man United in the league is a trip to Swansea City on Saturday afternoon.