Don was shocked when he finally found his brothers, after searching for them for quite a while. Hadn't they agreed to do something fun together to test out their new-found manly buffness? And there they were. And - oh! He had no idea they had such... ah... T-Their endowments surely deserved a closer look. For s-science. Of course.
That his brothers would notice him when he shot a thick load around the corner should have been obvious to his mind, but apparently even poor Donatello is helpless when his dick assumes direct control of his body. UwU/
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