Carolin Kennedy's pony was named Macaroni. I don't know if her little brother ever had his own pony.
Macaroni(No seriously it was, check wikipedia)
Yankee Doodle
Macaroni
John Kennedy's daughter, Caroline Kennedy, had a pony named Macaroni.
The pony's name wasn't macaroni, yankee doodle was talking about the feather and in the old days macaroni did not just mean pasta, it was a style of Italian dress. When he called the feather macaroni (a dandy) he was stating he was a gentleman of some social standing.
john f Kennedy
President Theodore Roosevelt's son Quentin had a pony named "Algonquin," . Once, when Archie Roosevelt was in bed sick, his brothers wanted to cheer him up. Quentin led his pony into the White House, down the hall and pulled it onto the elevator to take him to Archie's bedroom! I read about this before I even herd about the internet. Caroline Kennedy's pony, Macaroni, was a present from Lyndon Johnson. Macaroni roamed freely around the White House grounds and received thousands of fan letters from the American public. The photo of Macaroni with the Kennedy's on whitehouse.gov, looks to be on a white house porch, but there are no so exciting tales as Quentin's pony had.
The pony's name was Macaroni. Black Jack was the funeral horse which carried the backwards facing boots.
Macaroni
president Roosevelt had a pony.
....i guess it died...