Make the Mexican Wave

Pyth, 12 bytes

V+Gt_GXGNrN1

Demonstration.

In Pyth, G is the lowercase alphabet. +Gt_G is abcdefghijklmnopqrstuvwxyzyxwvutsrqponmlkjihgfedcba, the character that needs to be uppercased in each row.

V sets up a for loop over this string, with N as the loop variable.

In the body, XGNrN1 is a string translation function. X translates G, the alphabet, replacing N with rN1, the uppercase version of N. r ... 1 is the uppercase function. This gives the desired output.

C,73

Sometimes the simplest approach is best: print every character one by one. this beats a lot of languages it really shouldn't.

i;f(){for(i=1377;i--;)putchar(i%27?123-i%27-32*!(i/702?i%28-4:i%26):10);}

explanation

i;f(){
   for(i=1377;i--;)
   putchar(i%27?                 //if I not divisible by 27
     123-i%27-                   //  print lowercase letter from ASCII 122 downards
       32*!(i/702?i%28-4:i%26)   //  subtract 32 to make it uppercase where necessary: above i=702, use i%28-4, below it use i%26
     :10);                       //if I divisible by 27 print a newline (10)
}

Python 2, 69 bytes

i=25
exec"L=range(97,123);L[~abs(i)]^=32;i-=1;print bytearray(L);"*51

Nice and simple, I think.