LOUISVILLE, Ky. — On America’s ultimate dress-up day, Johnny Weir outdid everybody.

The former Olympic figure skater was resplendent Saturday on Churchill Downs’ wildly popular Red Carpet. Weir wore an all-white jacket and pants, white shoes with brown trim and a white and gold crown from which a long pink tail flowed over his right shoulder. “That’s my little pony,’’ he said.

Weir and Tara Lipinski, another former Olympic skater, served as NBC’s fashion and lifestyle reporters for the third consecutive Kentucky Derby. “I grew up around horses,’’ Weir said. “I rode Western and did showjumping.”

A man famed for his flamboyant persona and outrageous outfits also carried the Twitter banner for NBC. Later, America would see the awesome power of social media demonstrated literally. The plan was for Weir to wear a tweet-powered brooch in the shape of a small white horse on his lapel. The more “conversation” that was generated on the hashtag #WatchMeNeighNeigh, the faster the horse would gallop. Go, Johnny! Whoa, Johnny!

The late Jim McKay, ABC’s longtime Derby host, never could have imagined such a scene, except maybe in a fever dream.

For those obsessed with celebrities, the Red Carpet provides everything they want out of life, except for maybe a Kardashian sighting. Among the first to appear were Bob Guiney of “The Bachelor” and Star Jones. Jones’ escort (definitely not a celebrity) held a tiny white Maltese with a golden flowered headpiece. Star praised the Southern hospitality. Guiney announced his Derby pick [Nyquist] and that it was his 45th birthday.

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“And still single,’’ said a photographer with an Australian accent. He was annoyed he didn’t get a laugh. “Nobody got the joke,’’ he said.

Young women carried small boards with the celebs’ names written in black marker to ensure they would be recognized. You never can tell when “Used to be famous” might have kicked in.

Many NFL players did the walk, including the Jets’ Breno Giacomini, Lorenzo Mauldin and Bilal Powell and the Bills’ Richie Incognito. The Packers’ Aaron Rodgers and Randall Cobb and Cowboy Tony Romo showed up Friday night at the Barnstable Brown gala, the swankiest of all Derby parties, and were expected to arrive fashionably late.

An NBC reporter asked Mauldin about the green trim on his black dreadlocks. “When I played for Louisville, I wore red for the Cardinals,’’ he said. “Now it’s green for the Jets.’’

Incognito’s Derby pick: Gun Runner.

@Newsday

Why?

“I Iike guns.’’