I think they were put on the show, to show "diversity", just that. But Murhpy didn't count the love that fans expressed for Mike and Tina, so he obligated himself to write some meaningless storyline to keep public happy. So, when Murphy left Glee to write other projects, the new scriptwriters tried to realize how to…

And it would be certainly cancelled.

God, you read my mind with your comment…I completely agree

I don't know…this was the most disappointing episode they've ever done…It supposed to be (or at least, the fans waited for) the best episode ever, because it was the final episode of the Glee Club! However, there are a lot of unclear stories, meaningless actions in the whole episode…in fact, in the whole season 4 and…