The Doc thought for a moment and remembered that after a reversion the subject was highly open to suggestion for the first few minutes, so anything he said, the child should believe completely.
"Your funny, why would I be your daddy? I'm your boyfriend silly. Here come inside, we need to go down to my lab real quick." The Doc said leading the blond haired boy into the basement.
He continued talking to the boy as he prepared the gene reverser and a dose of the virus. "So, you want to be a strong swimmer when you grow up don't you?"
It took a few seconds for that thought to plant in the kids brain, "Sure do!" The doc hoped the imprint would help the virus when it went to work on growing the boy back into a man now that the boy leaned more toward fitness and swimming than he did before. The virus would accentuate those thoughts and grow them into his body.
"Ok Mark, this is going to pinch just a little." The doc said as he pushed the needle into his arm.
It only took a few minutes for the reverser, then the virus to kick back in as the Doc saw the boy start to grow.