One salamander mentions that John must play a special song to awaken Typheus, and after doing so, he will be offered "The Choice."
In one segment, you can fight a Bec-prototyped imp. It has a large amount of HP and teleports around, seemingly at random, but if you hold down space you can charge an attack that will momentarily stun the imp. When killed, it drops a sizable amount of Jade's Associated Item, uranium.
Killing the imp does not trigger any dialogue changes, but it will not respawn.
You can find a shop selling the following Fraymotifs:
Feathercadence, which costs 10,000,000.
Pneumatic Progression, costs 100,000,000.
Breathless Battaglia, costs 1,000,000,000.
Ivories in the Fire, costs 10,000,000,000, and indicated to be a combo move with Dave. Also a reference to Vriska's irons in the fire.
Mixolydian Maelstrom, costs 200,000,000,000, and indicated to be a combo move with Rose.
Fantasia's Inhale, costs 1,000,000,000,000, and indicated to be a combo move with Jade.
None of these can be bought, because John 'only' has 9,413,612boondollars, but they do offer amusing messages if the player attempts to.
Pressing CTRL+ALT+T or SHIFT+T in the mushroom farm area and entering "shoosh:doof" enables Trickster Mode and turns you into Dave. Hit CTRL+ALT+T or SHIFT+T again to revert.
The changes only apply to the 'battle' screen, but are remembered. If you leave and come back, you'll still be Dave.
On a sidenote: the 'riddle' of 'pap:nak' being analogous to 'shoosh:doof' can be solved by reading Sweet Bro and Hella Jeff. At the time of release, it could also be solved by visiting Andrew Hussie's Formspring account and seeing that when people posted the word 'pap', he would respond with the word 'shoosh'. Likewise, posts with the word 'nak' were responded to with the word 'doof'.
Go north to the right of the sign and you can find a grove of secret wizards.
During the fight with the Uranium Imp, players can hold space to fill the Mangrit gauge. Releasing space after it's completely full unleashes a more powerful attack, which temporarily freezes the imp due to the time powers of Fear No Anvil.
If you use Mangrit while controlling Dave, he performs a dashing attack, travelling back in time repeatedly for multiple hits. Naturally, this also freezes the imp.