Discover The Truth is a mysterious riddle added with the System Update. Solving it gets you a Illuminati Stone.
The "Kappa" Block can be earned by calling 411xx-41199 in a Telephone, only one number out of the 100 is reachable and different for each person.
Once you get the 19 different strings, you need to put them in a ROT13 Decipher and put them in the right order.
VGF QNATREBHF GB TB NYBAR GNXR GUVF NAQ FZNFU GUR YRSGJNEQ WRYYL JUVPU VF NGBC GUR JUVGR QBBE !
ITS DANGEROUS TO GO ALONE TAKE THIS AND SMASH THE LEFTWARD JELLYFISH WHICH IS ATOP THE WHITE DOOR !
"ITS DANGEROUS TO GO ALONE" is a reference to the first Legend of Zelda, where the old man gives you a Wooden Sword. You need to wear a wooden sword, place a jellyfish faced to the left above a white door and break it to get a "Kappa" block.
The "Edamame" Block can be earned by using Secret Of Growtopia to get this string :
SUPPORT means you need to go at http://growtopiagame.com/support and this is also hidden:
You need to shift each letter by the number in the string in the alphabet. You then get :
FIGHT VILLAIN WHO IS ON UPPER RIGHTMOST SPACE HEATVISION ICESHARDS SUPERSTRENGTH SHOCKINGFIST THEN RUN AWAY
Use a Henchman at the top right corner of a world, take these 4 cards and a random one, use them in ORDER, then press the run away button. Doing so will give you a "Edamame" Block.