Big Bird almost went on the Challenger space shuttle to teach kids about space.

The shuttle's explosion on January 28, 1986 killed seven crew members.

The beloved Sesame Street character wasn't on board because his costume was too big.

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Big Bird could have been on the Challenger space shuttle when it exploded on January 28, 1986.

One of the reasons why he wasn't? His costume was too big.

Caroll Spinney has played the beloved Sesame Street character since the beginning, and he told the story of his brush with spaceflight in "I Am Big Bird," a documentary about his life as the character, released in 2015.

"I once got a letter from NASA, asking if I would be willing to join a mission to orbit the Earth as Big Bird, to encourage kids to get interested in space," Spinney said in an essay in The Guardian in 2015. "There wasn't enough room for the puppet in the end, and I was replaced by a teacher."

Big Bird's costume is more than eight feet tall, and it was simply too big to fit on the Challenger shuttle. Tragically, high school teacher and trained payload specialist Christa McAuliffe took his place, and died along with the six other crew members aboard the shuttle that day.

NBC News reported in 2014 that NASA confirmed sending Sesame Street characters into space was a consideration, but never more than that.

"In 1984, NASA created the Space Flight Participant Program to select teachers, journalists, artists, and other people who could bring their unique perspective to the human spaceflight experience as a passenger on the space shuttle," NASA said in the statement. "A review of past documentation shows there were initial conversations with Sesame Street regarding their potential participation on a Challenger flight, but that plan was never approved."

Though Spinney didn't go into space as Big Bird, he still felt a special connection to the Challenger the day it exploded.

"We were taping another episode of Sesame Street at the time it went up and they said, 'The ship is about to take off so we're going to punch the broadcast of the takeoff onto the monitors on the set,'" Spinney told CBC News in 2014. "So we stopped working and watched the monitors, and when we saw it blow up, it was like my scalp crawled."

This story was originally published on January 28, 2016.