The remark came as Minister of State for Commerce Jairam Ramesh, who was concentrating on his reply during the Question Hour, said, "I thought the applause was for mango exports."
Prasad, who entered the House shortly before noon, was welcomed by thumping of desks by Congress, Rashtriya Janata Dal and other UPA members. The minister walked to the front row of treasury benches and shook hands with ministerial colleagues Shivraj Patil and Kamal Nath before taking his seat.
In the midst of the applause, BJP member Harin Pathak made some remarks against Lalu which were not audible, but RJD members and Ramdas Athawale (RPI) were quick to react saying the opposition should apologise, apparently referring to the minister's acquittal by a Patna court on Monday.
Stemming a possible confrontation between the opposition and the ruling benches, the Speaker said, "Both mangoes and Laluji are sweet," drawing peals of laughter.
Ramesh earlier said Japan has lifted a 20-year-ban on import of Indian mangoes by allowing six varieties including 'Alfonso', 'Langra' and 'Chausa' to get into its markets.
Negotiations were on with Australia and New Zealand for expanding mango exports, the minister added.