According to WENN, Downey Jr., who is currently filming the Sherlock Holmes sequel, is part of an entire image makeover for the brand.
Kris Wixom, the creative director behind the project, revealed that Downey Jr. was chosen because of his "everyman suaveness", as well as because he has "a voice that could wear the top hat, monocle and cane and still feel contemporary and cool".
The company considers the campaign to be "new retro", returning to an "old school" concept, reports The New York Times.
"One thing we learned is that while people love Mr. Peanut, they weren't connecting with him beyond the nostalgia," said Jason Levine, senior director for marketing at Planters. "Having him able to speak is bringing him to life as a personality, and people can engage with him more."
The new ads featuring Downey Jr. begin on Tuesday in the United States.