When a form of media or literature is so perfect (i.e The Sonic Movic) experiencing any other entertainment leaves a sense of dissatisfaction and disappointment.
"Just saw Upward and when it ended I could only think about how nothing can compare to seeing Sonic in theaters"
-Thomas A.(First Recorded Example of the Sonic Effect)
The Sonic & Knuckles Effect only happens when 2 characters are compared to each other. One character may have more careless, goofy, "radical" behavior, and the other character may have serious and focused behavior. The original form of the Sonic & Knuckles Effect was, well, Sonic & Knuckles, with Sonic being the more careless character, and Knuckles being the more serious character.
Person 1: Hey! Cmon, what are you doing here just sitting around?
Person 2: I'm trying to look after my belongings.
Person 3: It looks like you two have the Sonic & Knuckles Effect