Star Trek: Federation Starships by BarkerC

Question 5

In the Season 1 TNG episode "Conspiracy", art director Mike Okuda makes a nearly impossible to see in-joke by creating at least two starships based on other works of fiction. One is the USS Heart of Gold with registry number NCC-42. What literary character was honored with the name of the starship bearing the hull code NCC-221B?

USS Sherlock Holmes