Basically, copy and paste the reply above you and you can either add, take or change a letter from it, it doesn’t have to make sense!!!
For example:
A: Hello, from the dark side.
B: ello, from the dark side.
C. ello from the dank side.
D: ello forom the darnk side.
I’ll start:
She sells seashells by the seashore!
He sells seashells by the seashore 
He seals seashells by the seashore
He seals seashells by the seashores
Must the sentence make sense, or can it be something completely stupid? 
It can be something that doesn’t make sense.
He seals seashells by the seeashores
Okay 
He heals seashells by the seeashores
He heals seahells by the seeashores
He heals seehells by the seeashores
He deals seehells by the seeashores
He duals seehells by the seeashores
He duals seehells by the seeachores
He duals seehells by the seekchores
He dials seehells by the seekchores
Ze dials seehells by the seekchores
Zen dials seehells by the seekchores
Zen dials seehells by the seekchoires
Zen dials seehells bye the seekchoires
Zen dials seehells bye tie seekchoires
Men dials seehells bye tie seekchoires
Men diels seehells bye tie seekchoires