Earlier this week we shared photos of Glee cast members playing other characters on the show.

Now, in a new spoiler report, we’re learning what happens in the plot that causes these swaps.

TV Line has learned it’s part of a special double-episode to air on May 15th:

Sources confirm to TVLine exclusively that the network is combining the show’s 20th and 21st installments into one, two-hour episode on Tuesday, May 15.

But it’s the first of those two hours — which finds New Directions planning for the annual competition — that is likely to generate the most watercooler chatter. That’s because in the midst of rehearsing their new routine, Tina (Jenna Ushkowitz) suffers a mild head injury and begins to experience a different — yet oddly familiar — alternate reality.

Do you like this plot line or is it way too odd? We’re going with the latter.