15 Saddest How I Met Your Mother Episodes

In season seven's Symphony of Illumination, Robin suspects she may be pregnant with Barney's baby, and the episode sees her take narrating duties from Ted and telling her own future kids about how she reacted to her pregnancy.

At its core, it's actually quite funny, with Robin and Barney becoming increasingly on edge about the thought of having and raising kids. Their worries are quickly put to rest though when a trip to the hospital reveals she's not actually pregnant. Though this makes her happy, since she never wanted kids, Robin later learns a heartbreaking truth - she can't have kids at all.

At first okay with the news, Robin soon comes to realise that she always liked having the option, and now any possibility of a future family has been shut down. The episode ends with Future Robin admitting her "kids" aren't real, and sees Ted swoop in to cheer her up with an epic light display. It's a tragic reveal to end on, and still stands as one of the show's most daring plot twists.