Dreamcast [Old] - Did You Know Gaming? Feat. Brutalmoose
If the player enters the following names starting with the word "Krunk" as their profile name, hidden messages will appear:

Krunk: "You heard about the time I killed me a couple of Heroes?"
Krunkl: [same message as above]
Krunki: "My hands are red with the blood of thousands."
Krunko: "You know I once burned down a whole village?"
Krunkn: "I once killed a White Balverine, I did. It's true."

Note that the last letter in each variation of "Krunk" spells "lion", in reference to Lionhead Studios.
Contributed by MehDeletingLater
NSFW - This trivia is considered "Not Safe for Work" - Click to Reveal
The Demon Door located in Witchwood Cavern will only open to those that know his name, by striking the four Witchwood Stones labeled with a letter nearby to spell it out with a voice saying each letter. The door's name is "HITS", but if you spell "SHIT", the voice will say "Shit" and cause two Balverines to appear and attack you, although these enemies will only spawn the first time you do this.
Contributed by MehDeletingLater
In the Anniversary Edition, the DLC helmet, "Dave's 'Mind Crate' Hat" is a reference to the game Minecraft.
Contributed by ThisGuyInTheSuit