A selection of illustrator and writer Hilary Knight’s artwork, including the original portrait of Eloise, will be auctioned at Bonhams New York on Dec. 5. It’s estimated to fetch between US$100,000 and US$150,000.

Depicting whimsical Eloise—one of the most influential children’s book characters—in black, white, and pink, the portrait was painted by Knight as a birthday gift for Eloise’s co-creator Kay Thomson in 1956, on the eve of her appearance on Person to Person on CBS, where Thomson showed the painting to the program’s guest host Jerry Lewis.

Shortly after, Thomson, a resident at The Plaza Hotel where her fictional character Elo...