I just collapse into a mess of tears every time I watch this episode.
To those that don't watch the show, the character pictured, the Ice King, is a princess kidnapping (yet more and more sympathetically portrayed over time) maniac who has a crown that gives him magical ice powers. It was revealed later on in the series that the crown actually also keeps him immortal while chipping away at his sanity, and that he was once a perfectly sane man who drove his lover away with his increasingly erratic behavior. He lived through a nuclear apocalypse (The show is set a long amount of time after said apocalypse, I believe around a few thousand or so years) and, before he was fully transformed into his current state, had helped one of the show's other characters, Marceline, through the post-apocalyptic landscape not long after the war, when she was still a child and could not fend for herself from the weird mutated monsters attacking. (Marceline is also immortal, in a teenaged body and seemingly mind too, as she became a vampire at some point or was possibly born as a vampire) The episode which this title card belongs to centers on Marceline's desperate (and ultimately failed) attempts to try and bring back the Ice King's memories of when he was sane and still known by his real name, Simon. What really helps drive it home is that she's had to watch him lose his memory and mind and go more and more crazy as the show goes on, yet she used to see him as her father figure and it appears from this episode that he may never gain any recollection of his past life, real name, or former personality, even as he directly stares at artifacts from his past. There's this really sad musical sequence towards the end that just destroys me every time I see it, but every time I try to look for it on YouTube, I either find a cover version of it or it's shortly taken down afterwards. So take me posting this as a bit of inspiration to you to try and watch the full episode somewhere on the internet or whatever now that you have some backstory on it. I-if you want to...
Also, that image that didn't do anything to me when I was younger? Didn't cry, but it definitely gave me feels. I'm a softie now, aren't I?