The "Fun-Guy" cube is thematic, hankering back to my childhood when my favorite deck was green Thallids. This cube contains:

Every Fungus ever printed;
All Celebration, “Party”-matters, and Proliferate cards;
All cards with the consecutive letters “fun” anywhere in the card text;
Most cards with “f” followed by “un” in the title (to fill out certain colors).

It is a singleton cube, except for 4 Thallids and 4 Thorn Thallids.

Primary color themes:
W - lifegain
U - counterspells, proliferate
B - small-game control
R - sac creatures to deal direct damage
G - creature abilities, go wide

Roughly ⅓ of the cards are common, ⅓ are uncommon, ⅓ are rare/mythic.

Fixing: all 10 Talismans, 10 shock lands (Ravnica), 5 storage lands (Time Spiral), 5 scry lands (Theros), plus assorted artifacts and green mana dorks.

Fun Facts:
There are a handful of bad, old cards in the cube. Deal with it! Have fun. Play a couple of them and tell your friends stories of your epic victory with Raging Bull.
In paper, there are 41 of each basic land in the cube’s land station, 41 Clown Robot tokens, and 41 Saproling tokens. See if you can figure out why!

Rule 0s:
There are 8 Attractions in the cube. Attraction side decks only require 1 Attraction. All 28 cards with “fun” (no spaces) in the title have the ability:
ETB, open an Attraction.

One card has “venture into the dungeon”. The only dungeon is Lost Mine of Phandelver. (It's the only "fun" dungeon.)

Some Un-cards call for Name stickers. Every Name sticker says “Fungus”.
All other stickers must come from the Space Fungus Snickerdoodle card.