Factual error: While they're eating dinner, Deena says "I can't believe this is happening" to which Curtis says "you made it happen! you are the queen of Disco!" The error here is that Diana Ross didn't sing disco until after she went solo, in 1970.
In the scene where Effie sings "Curtis, this time Effie's gonna win", Curtis turns his head a little to his left when Effie sings "win" at his face. But at the next shot, camera behind Curtis, Curtis' head is slightly turned to his right.