My 5 year old is doing naughty things that isn't normal, what do I do?

I wouldn't be to concerned for all children at some stage are fascinated and inquisitive with their private parts. It sounds like he was just showing off in front of the baby, while waiting for you to get him some pants.

A 5 year old can understand what is wrong from wrong, try talking to him calmly (not angrily) explaining that playing with his willy in front of the baby is wrong.

When children show each other their private parts or even touch each other, it is not an automatic sign of anything more than curiosity. Adults should treat it matter-of-factly and use it as a moment to teach children that private parts are private and that behavior of this kind is not appropriate.

Well, young kiddies find no end of humour out of body parts and body functions. But seeing this has come up maybe it is a good time to talk about privacy and what is acceptable!

This behaviour can often come from older kiddies so it might be good to question and try to find the source. As suggested though, remain calm and do not get upset if questions come your way!

Well, kids these days are very smart and most of the times we underestimate them. I think the kid has certainly watched something from the older kids in the neighbourhood or on the internet or the television. They have a very high grasping power and usually absorb everything that they hear or see. They don't have the power of classifying the information they absorb. It is always better to talk to them openly about such things and educate them and discourage them from doing it in the future.