3 added 9 characters in body
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C (gcc), 5050 49 bytes

i[]=i[8]={0,1,1,1,2,2,3,3};f(char*m){m=m[i[rand()%8]];}

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C (gcc), 50 bytes

i[]={0,1,1,1,2,2,3,3};f(char*m){m=m[i[rand()%8]];}

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C (gcc), 50 49 bytes

i[8]={1,1,1,2,2,3,3};f(char*m){m=m[i[rand()%8]];}

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2 added 49 characters in body
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C (gcc), 3550 bytes

fi[]={0,1,1,1,2,2,3,3};f(char*m){putchar("ABBBCCDD"[randm=m[i[rand()%8]);%8]];}

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C (gcc), 35 bytes

f(){putchar("ABBBCCDD"[rand()%8]);}

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C (gcc), 50 bytes

i[]={0,1,1,1,2,2,3,3};f(char*m){m=m[i[rand()%8]];}

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1
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C (gcc), 35 bytes

f(){putchar("ABBBCCDD"[rand()%8]);}

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