Yellow Snow

Quagmire: "Hey, maybe we could set Peter up with another lemon snowcone."
Peter: "The first one didn't taste like lemon at all. It tasted like..."
Peter: (pauses)

Peter: "Oh, you guys are asses."

—from Family Guy

When you see snow outside that's ominously yellow-colored. Or worse, when someone tries to feed you a "lemon" snowcone. Yeah, this is a Toilet Humor trope. Sometimes hilariously combined with a character's own moment of Fridge Horror when they realize what it actually is.

Due to this trope's inherently juvenile Refuge in Vulgarity, it is unlikely to be appreciated by anyone older than 25. Or Frank Zappa.

Examples of Yellow Snow include:

Advertising

The USA commercial for Rayman 3: Hoodlum Havoc uses this trope. It begins with two snowboarders who appear to be urinating in the snow, writing their names, and then we hear a wave-like sound in the distance as the camera focuses on the snowboarders staring in awe. The camera then turns to a bank of snow with the Rayman 3 logo written in urine, and Rayman looking at the camera, smiling. Then the commercial ends revealing that the snowboarders were actually squirting yellow liquids out of canteens.

Film

The Winter Olympics special on Top Gear had two challenges between James and Jeremy; the loser of each would have to partake of the yellow snow. Each lost a challenge, so each got to "enjoy" their prize.
In Frozen, Olaf the snowman warns Anna and Kristoff against yellow snow.

Live-Action Television

Christmas on Vesterbro has it in the theme song. "Alt kan ske når det er jul/ selvom vores sne er gul" (translated: Everything can happen when it's christmas/ even though our snow is yellow).

Music

Frank Zappa's "Don't Eat the Yellow Snow" tells the story of an Inuit boy named Nanook, his favorite baby seal and a fur trapper. And, of course, the yellow snow.

Newspaper Comics

In Channel Ate, one character offers another lemonade with a wink. The second character promptly refuses to drink it.

Recorded Comedy

"Bear Whiz Beer -- It's in the water; that's why it's yellow!", a mock commercial from Don't Crush That Dwarf, Hand Me The Pliers by The Firesign Theatre.

Video Games

South Park the game on the Nintendo 64 had snowballs as the default attack. A special use for them is to take a whizz on them (with pants unzipping sound) then let fly. Hit one of the four kids with this and enjoy the creative Cluster F-Bomb retaliation.

Western Animation

In Family Guy, Peter's friends give him a "lemon snowcone".
Yeti's mysterious "lemon" snowcones in Monsters, Inc., which he offers to visitors. The frigid remoteness of the Yeti's home and the Yeti's chronic isolation are...not reassuring.
In an episode of SpongeBob SquarePants, Patrick ate yellow sand.
In The Venture Brothers, Dr. Venture is left stranded and naked in the high Arctic by his paranoid Poisonous Friend Richard Impossible. As he's wandering through the frozen plain, he abruptly steps into polar bear urine, and angrily laments how he has the bad luck to step into the only patch of Yellow Snow for miles around.