Ignatius "Iggy" Thistlewhite (named Ignatius Heppelwhite in the original version of the poem) is a character in the book The Year Without a Santa Claus and both of its television adaptations. In the original poem, he is stated to be six years old and is the only child in the world who is not upset that Santa Claus is not delivering Christmas presents this year, because he knows that Christmas is about giving, and thus he believes that Mr. Claus deserves to take a break. When he explains this to his classmates, they take his words to heart and all send presents to Santa.
In Rankin/Bass' animated adaptation, Iggy is a resident of Southtown, where he lives with his parents (who were not mentioned in the book) and an unnamed pet dog. He has a larger part in the story due to the expanded plot, and also appears to be a few years older than his six-year-old counterpart from the book, because when he first appears, he and his classmates have all decided that they don't believe in Santa Claus anymore. (This is despite the fact that, since the newspapers were reporting about Santa taking Christmas Eve off, Santa's existence isn't something that would be questioned or denied in-universe.) As such, they initially show no remorse about Christmas being canceled, much to the dismay of the elves Jingle Bells and Jangle Bells, who came to Southtown looking to find Christmas spirit. But when an undercover Santa comes to the boy's house for information on the elves' whereabouts, Iggy's mother invites him inside to take care of his cold. Over a conversation with tea and a song reminiscing about the joys of Christmas, Iggy comes to believe in Santa Claus again and soon figures out that his new friend is that same jolly old man.
On the advice of his father, Iggy teams up with Jingle and Jangle to plead their case of getting Vixen out of the dog pound to the mayor. When their attempt is sidetracked, Iggy is taken on an adventure by Mrs. Claus and the elves to the realms of Heat Miser and Snow Miser. After Mother Nature convinces her two sons to compromise, Iggy is brought back to Southtown and is later shown among the kids making presents to give Santa. Later, when Santa is shown parading through Southtown on Christmas Eve, Iggy is seen waving at him. At the very end, Iggy is last seen giving his parents their presents and riding a new bike that he received from Santa.