15 Saddest How I Met Your Mother Episodes
12. Band Or DJ? (Season 8, Episode 13)
Though season eight's Band or DJ? has a hilarious sub-plot involving Barney's attempts to get Robin's terrifying father's approval to marry his daughter, the second plot of the episode sees Ted throw himself into planning Barney and Robin's wedding and trying to get a DJ for the reception. Though this sounds like typical HIMYM fun, things take a turn when it comes to light Ted is just keeping busy to deal with his conflicting feelings about the marriage.
Realising he still loves Robin but is too afraid to admit to something so horrible, Lily gives him a tough talking to, and gives audiences her own admission - that sometimes she wishes she had never become a mother. It's an honest reveal, played to heartbreaking perfection by Alyson Hannigan, and allows Ted to reveal his true feelings about the upcoming nuptials and his feelings for Robin.
On the plus side, the episode does end up with a the Mother's band being hired, setting in motion her and Ted's meeting.