Most of the time, it is Calvin doing the mischiefs bugging his parents. This time it is the Dad who is bugging Calvin and Mom. Check out the reaction of Calvin and his mom in second last strip. The best is the conversation between Calvin and his mon in last strip :-
Calvin - Just how long did you know Dad before you married him?
Mom - There's one in every house
He he.... that means it would not have made any difference if she would have found some other guy to marry. All men are same.
Yes very true.... Men are Men..... :)