When Mondo Burger begins to implode, the customers are bewildered as to what's going on. Since the movie is set in California, you'd think they would assume it was an earthquake.
Ed proves himself as Obfuscating Stupidity. He reads the contract, and while doing so points to specific spots as though he were actually understanding it. Further, Dexter tells Ed exactly what the contract states: 20% of Ed's sauce-based profits goes to Ed; the other 80% goes to Dexter. Ed, then, probably knew full well that he was being ripped off by Dexter (20 cents for every 10 burgers sold). And he still signed the contract, in order to make a friend and help someone in need.
Fridge Brilliance: Mondo Burger's additive enlarges the burger after heating. Too much additive causes the burger to explode. Boyle's Law (PV=nRT) would suggest that the additive, then, turns into a gas upon heating. This is because the temperature (T) and gas constant (R) are constant, the amount of chemical in the gaseous state (n) is the independent variable, the volume (V) most readily changes as a dependent variable, but when the volume can't increase any more the resultant change in pressure (P) causes a burger explosion.
This also explains why the dog wouldn't eat the Mondo Burger: if it simply added meat-mass then it would smell and taste like real meat because it would be real meat.
Fridge Horror: Mr. Wheat got out of his car only mere seconds before the giant burger from Mondo Burger's roof fell on it.