A challenge where you put a bunch of mentos in your mouth and trying to consume a 2 liter bottle of diet coke spilling as little as possible. The chemical reaction produced by the coke interacting with the mentos causes it to burst out causing people to spill coke while consuming it.
"Chester and I tried the Diet Coke and Mentos Challenge last night, man it hard to chug down that Diet coke tho!"
Immortalized by an Eddie Murphy bit, "Have a Coke and a Smile" was a Coca-Cola ad campaign in the early '80s.
In Eddie's bit, Richard Pryor tells Bill Cosby (who did Coke ads) to "Have a Coke and a smile and shut the fuck up).
Richard: Do the people laugh when you say what you say?
Eddie: Yes.
Richard: Do you get paid?
Eddie: Yes.
Richard. Then tell Bill I said have a Coke and a smile and shit the fuck up, the jello-pudding-eating motherfucker.
When you enter a public restroom and it's so disgusting that not only do you lay a seat cover down, but you hover over it too.
"I went to the public restroom at the beach and I couldn't tell if the seat had water droplets or pee droplets on it, so I decided to cover AND hover."