Clearing the high 3 bits of the PPU $2001 register improves brightness in some games.
01C9C4:
09 18
Database match: Felix the Cat (USA)
Database: No-Intro: Nintendo Entertainment System (v. 20180803-121122)
File SHA-1: D98426B4955AE9EC4FEAEDB2538AAB35B8209C06
File CRC32: 639E88E
ROM SHA-1: CC03A83C6AD9BBB858EE5FF04E9E7B2362EEA06A
ROM CRC32: 2CAAE01C