Is it true they were/are considering making a spin-off series called "Jack & Karen"?
No, this is in no way true. Near the beginning of "Will & Grace", and even now, people have believed that the show would be much better if secondary characters Jack McFarland and Karen Walker became the leads in "Will & Grace" and that the show should be renamed "Jack & Karen". But all members of the cast have said, at different times, that without Will and Grace around, the show would lose much of it's heart, and Jack and Karen would be too much to handle on their own. And according to Eric, fans who really believe that Jack and Karen should have their own show can "go and finance that show".
Are Megan and Sean dating?
No, despite their obvious closeness to each other, Megan and Sean are not and never have been dating. They are just very close friends, which causes some people to think that there must be more to their relationship.
Is Sean married and does he have any children?
This is usually brought up when people ask if Sean is gay. All I know for sure about it is that Sean is not married, nor does he have any children, though he does have at least one niece whom he is very close to.
Is it true that Sean and Megan originally auditioned for the parts of Will and Grace?
Yes, both Sean and Megan tried out for the leads. Sean originally auditioned for Will Truman, but when Eric was cast for the part, Sean tried out for Jack and scored the part when he walked out of the room and said to the producers "now don't be checking out my ass". Apparently, that's when the producers knew that Sean was perfect for Jack. Megan went in to audition for Grace, but felt the audition didn't do well and was sitting at home eating breakfast when her agent phoned to tell her the producers wanted her to try out for Karen which she got by adding her own little things, such as the voice and the word "honey".
Was Megan in Old Navy commercials?
Yes. Megan appeared in several commercials for Old Navy a few years ago, many which appeared during "Will & Grace". She was usually see surrounded by four or five young men.