Forgot passcode to Apple TV

Apple TV does not require a Passcode. You do need a Passcode to access a service such as AirPlay and you do need a Password to your Apple ID to access iTunes, Stores and iCloud Photo Library.

ATV 4 is a streaming device. It has very little stored on it, so erasing it should not be a big problem.

Otherwise, provide us with more detailed information so that we might be of more help.

Which passcode do you mean. If you mean the one for AirPlay, just disable AirPlay passcode and then enable it again.

Do you mean the passcode for parental control? If so, you may have to reset ATV and re-enter your information.