The act of deficating into a toilet bowl already spackeled with human feces. Fernando is that Mexican dude with a fecal fetish that just can't seem to get enough poo in his diet. The spackeling found in toilets refers to the remnants of Fernando's turd-log fetish which commonly adorn the corner of his lips. Fernando is a smallish Mexican man in love with himself, and his jet-setting life and will do anything in his power to fuck over the next guy in line to get what he wants. He's the backstabbing, shit-eating little douchebag that everyone hates.
Bruce: Oh god! (stomach rumbling)
Vince: What's wrong man? Did that pile of carne asada do a number on you, or was it the sauce you used to add all that flavor?
Bruce: I'm not sure, but if I don't go and "Feed Fernando" soon, I'm going to paint the inside of my underwear with a stream of butt coffee!