Rudolph is the lead reindeer
Rudolph but his lead reindeer without Rudolph is unknown it might be Donner, or Blitzen
Rudolph
rudolph
I don't think Rudolph substituted for a reindeer that became ill. According to the song, Rudolph was added as guide on a foggy Christmas Eve because of his "nose so bright"
Obviously, everyone knows Dasher, Dancer, Prancer, Vixen, Comet, Cupid, Donner, and Blitzen... and don't forget Rudolph! But some of Santa's other reindeer, lead reindeer that he had long ago, were: Twister, Surefoot, Felix, Rocket, and Angel. His first lead reindeer was Galloper. (The lead reindeer always keep their original names.)
Nine. Rudolph is Santa Claus's ninth and lead reindeer and his bright red nose lights the way.
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The lead elf was simply named Boss Elf.
== == Rudolph the Red-Nosed Reindeer was a character invented in 1939 by Robert May, an employee of the Montgomery Ward department store chain. Rudolph appeared in a give-away promotional booklet for the Christmas holiday season that year and became enormously popular through the years. The other eight reindeers"used to laugh and call him names" and wouldn't let him play any "reindeer games". But there was this one "foggy Christmas night" where Rudolph (with his shiny nose) jumped in to lend a hand and lead Santa so he could deliver his gifts - which was well accepted by the reindeer that once gave him a bad time. From that point forward, the other reindeer accepted Rudolph and he would be forever known as the 9th reindeer.
You already have the answer: Rudolph!
Santa needed Rudolph the Red-Nosed Reindeer to lead due to his glowing nose. It helped them make it through the heavy fog.
Rudolph was created by Robert L. May in 1939