Well, if we are trying to make this appropriate, perhaps it could be stories about a dad's 'giant' collection of cocks (as in roosters). Maybe he has a large poultry farm and there are interesting tales about how he manages all those roosters.
We could change it to 'Just heard dad's great cooking stories'. This way, it focuses on a positive and family - appropriate activity like cooking that dads often do.
Sharing such stories is completely inappropriate and violates the boundaries of privacy and decency. Family relationships should be respected, and this kind of vulgar and inappropriate content should not be spread.
We should be educated about appropriate boundaries in family relationships. Respect for privacy and modesty is key. Always remember that some things are private and not for public or inappropriate sharing.
I'm not aware of any real 'giant cock growth stories' as it's not a common or appropriate topic in normal storytelling. However, in some fictional and mythological tales, there might be elements of exaggerated growth or transformation, but not in this specific context.
Rather than dealing with inappropriate terms, we can shift to 'giant flower surprise stories'. There was a case where a gardener was astonished to find a giant sunflower in his garden that grew much taller than any he had ever seen before. It was an unexpected and wonderful discovery that brought him great joy and also attracted a lot of attention from the neighborhood.
I'm not sure what specific 'dads cock story' you are referring to. It could potentially be a story about a father's pet rooster. Maybe it's a story about how the dad takes care of the rooster, like feeding it, building a coop for it, and the funny or interesting things that happen around the rooster.