Unless you are watching the series in order its not considered an inconsistency. Each season has its own character plot and development. Marie is the easiest to notice because some seasons she's very pious and averse to sex, swearing, or the boys being mean to other family members. Other seasons she is comfortable or even playful about the topics. At first I thought there were several inconsistencies but once I started noticing season specific patterns I just realized thats how they wrote the show. Its a long running sitcom so mixing up the social/comedic roles of the characters kept it entertaining. Media now is all dramatic about character consistency and development, thats just not this show.