There is a goof both in Pilot and this episode. When Tori has her locker done, the red locker beside it moves to the very end and the green-ish locker that was in the very end (to the right) isn't in that spot anymore when Tori makes her locker.
After Tori's 2nd attempt at the bird scene, where she gets the backdrop and plastic bird, she goes to Cat for help. before, when it does the bit of music and the zoom of the school, you can clearly see that Tori's locker is decorated, though after her encounter with Cat, Beck comes to her locker, where Tori's Locker only has the stripe. In the Cat encounter it has the whole "Make it shine" decoration.
When Sikowitz throws a ball at Tori, but misses, the two are then seen together, and the ball is right next to Sikowitz. That ball was blue, the one he had thrown at Tori was green.
When Sikowitz threw the ball at Cat at the beginning, Cat would've got a red ball mark but it doesn't appear. Or she would have got dizzy (pending by how hard the ball was or the pace).
There is no way Sikowitz could have thrown the ball at Cat the second time because in the previous scene with Tori not only was there no ball near him but no way he could have found the ball in the limited amount of time between the scenes.
It was lunchtime after Sikowitz's class, which usually means that it was fourth period, but in Pilot, Sikowitz's class was first period.
When Beck, Robbie, and André are talking at lunch, Beck is picking up his coffee. When the camera switches to a different angle, his coffee is back on the table and he is picking it up again.
At the beginning of this episode, when André and Robbie are going down the stairs, you can see André's belt was raised up, but the other scene it doesn't show. However, when they reach the bottom of the stairs, it's raised up again and shown.