Ernest Greeves is a character in Layton's Mystery Journey: Katrielle and the Millionaires' Conspiracy. He is an assistant of Katrielle Layton who keeps the agency in tip-top shape and heeds Katrielle's every beck and call. He has a massive crush on Katrielle. Ernest is also known for solving puzzles and being somewhat of an academic, attending one of the top universities in England on a scholarship.
Ernest first met Katrielle after he was wrongly accused of stealing research of a world-renown professor, Dr. Gene Ohm. He was being questioned by Inspector Hastings when Katrielle promptly barged in on the interrogation and stood up to the Inspector for him. After learning that Ernest was a first year at Gressenheller University, she accompanied him back to Gressenheller to prove Greeves' innocence and also knock out a bit of business she had at the school. After retracing Ernest's clumsy steps through goat poo, rosebushes, and a stroke of bad luck, Katrielle was able to piece together that Ernest was innocent- Dr. Ohm hadn't been able to finish his research, fed it to the goats, and then pinned the blame on Ernest. After Katrielle managed to clear his name, Ernest begged to be her assistant, hoping to repay her somehow.
- He is 19 years old.
- His first name, Ernest, might come from the term "earnest", meaning "serious". His last name could come from "grieves". This could mean he is very seriously grieving about something.
- His hobby is to study flowers.
- His dream university is Gressenheller University.