As some fans had been hoping, Psychonauts 2 has some nice little nods to Brutal Legend, another cult classic from the studio.
Both of the easter eggs in Psychonauts 2 focus on the Brain in a Jar character, which makes sense considering that he is voiced by Jack Black, the voice of Eddie Riggs in Brutal Legend.
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The first easter egg is a pretty subtle one but is absolutely purposeful. During the Brain in a Jar level, you'll be tasked with looking for Vision's violin in a level made up of massive eyeballs. After platforming your way to the end, Raz will be able to interact with the violin to pick it up. Each instrument that Raz collects has a unique animation that mostly just has him dancing, but this one is a bit different.
When Raz picks up the Violin, it's embedded in the ground. He pulls it out, lifts it into the air with one hand and loudly shouts "yeah-heh-heh" as lightning strikes it from above. This is a callback to the opening scene of Brutal Legend, where Eddie Riggs pulls out the Separator from the ground, with Raz doing his best Jack Black impression.
The next easter egg can be found at the end of the game. If you go into the Central Nerve, you'll be able to find the Brain in a Jar sat around the Psychonauts headquarters. Using Clairvoyance on him reveals that he sees Raz dressed up as Eddie Riggs. Raz is wearing the same clothes, vest, bracelet, and even has a little chin strap similar to Riggs. It's a nice nod to Jack Black's previous character.
Psychonauts 2 referencing Brutal Legend shouldn't come as too much of a surprise considering that game also did the same for the original Psychonauts. One character, voiced by Richard Horvitz, could be found wearing Raz's glasses, whilst Kabbage Boy is shown using Raz's victory dance in the opening cutscene of the game. You could also put Raz's face up on a mountain if you so desired.