21

Like 73 in Chrome's Show of Chromeyness, 21 is a number which appears often in That Cool Show That Makes No Sense Whatsoever. A reference to the viral meme, it has appeared in many episodes, and is often unnoticed by the characters and viewers. It has currently appeared in every episode except A Tale Of Two... Well, Something and Chocolate  Milk Just Chocolate.

Plungin' the Dungeon

 * The number can be seen written numerous times on the wall.

Toilet Floods and Rubber Ducks

 * Chocolate Milk says to Kyle he's flooded the toilet 21 times already this year.
 * When the trio fly by a convinience store, the number is written in huge letters almost covering the full screen for one frame.

The Completely Random Parade

 * There is a constellation seen in the sky throughout the entire episode that spells 21.
 * Everyone in the trio screams in this episode; all for 21 seconds exactly. This is considered the hardest one to find.
 * When Chocolate Milk gets repeatedly attacked by a Mars Bar, he exclaims that he's being doing this for around 21 years.

Chocolate Milk All Over my Book

 * Whenever Chocolate Milk opens a page, it always says "Page 21" at the bottom.
 * When Chocolate Milk is selling his book, one of his fans say "I've been waiting 21 weeks for a signature!".
 * Another says "I'm 21 times bigger than your other biggest fan!".

Prank Calls

 * When Circle decides to get a snack, he says "I'm getting a snack. We've already done like 21 prank calls, we should stop for a break".
 * Everyone in the other trio says they are 21 years old.

Smell you Later

 * When Circle finds a book on how to restore magic milk, the book says that they only have 21 seconds to save the person when their milk turns pink.

Chocolate  Milk Just Chocolate
None.

Van Mania, Part 1

 * Kyle wishes for 21 arms.
 * Chocolate Milk wishes to be 21 times faster.
 * Circle wishes for 21 more wishes.

Van Mania, Part 2

 * While Circle is sleep-talking, he briefly mutters "9+10 *yawn* 21"
 * When the trio are sent to the moon, Kyle says this is 21 times worse than anything they've ever done.

The Dynamite Stick

 * When Scchpork asks for the trio's assistance yet again, Chocolate Milk screams "21 TIMES IN AN HOUR!"

So Bubble
TBA
 * When Circle starts blowing bubbles in various shapes, he makes two, one in form of a 2, the other a 1.