- After Marty burns the Almanac, thus preventing Biff from ruining the future and murdering George, the newspaper declaring George dead changes to him receiving an award, and Marty just about explodes with joy. Then the paper Doc has that says "EMMETT BROWN COMMITTED: Crackpot Inventor Declared Legally Insane" changes to "EMMETT BROWN COMMENDED: Local Inventor Receives Civic Award", and Doc smiles as he declares, "Mission accomplished!"
- The fact that what started everything was the fact that Doc wanted to save his friend's (Marty) future family is rather endearing. Also, it's never confirmed in dialogue, but it's heavily implied Doc wanted Marty to pick up hints about the accident that crippled him and turned him into such a broken old man so as to prevent that future from happening.
- Speaking of Marty's future as a broken old man, there's the fact that despite what he made of himself, Marty's parents are still on visiting terms with him. Whether he's famous or not, whether he's the rock star he always wanted to be or not, his parents are supportive of his life.
- This also counts as a Tear Jerker, but the reason Marty was so devastated over the loss of his father in the new timeline? He'd recently gotten to know his old man better for a week. In that time he learned how much they had in common, and that they were both insecure teens, and (depending on your take on the films' use of Ripple Effect-Proof Memory) was looking forward to getting to know the man he inadvertently helped his father become.
- When Marty gets the letter from Doc. The way he just lights up when he sees who it's from, and his pure joy at the knowledge that Doc is still alive somewhen is just so brilliant.
- When Marty explores the 2015 Hill Valley, he sees that the clocktower is still at 10:04 PM from 1955. Nice to see that the Hill Valley Preservation Society succeeded in 1985, and that they're still working hard in 2015 and beyond.
- Meta-example: This video done in conjunction with the day Marty goes into the future, featuring Doc Brown himself (played by the original actor).
- Despite the fact that he's on a life-or-death mission, Marty still can't resist stopping to stare adoringly at the younger versions of his parents falling in love when he ends up at the Enchantment Under the Sea dance once again.
- After Marty has swiped the Almanac back from Biff, he tries to use the hoverboard to get away, but it can't go anywhere as fast as Biff's car. The car roars down on Marty, Biff grinning as he prepares to run him over...and then Marty disappears upwards, saved by a line Doc dropped him from the DeLorean, as the music soars.
- It's subtle, but after meeting back up with Marty in 1985!A, Doc doesn't call out Marty for indirectly causing Biff's rise to power, telling him "it's all in the past"... There's also Doc knowing Marty would go to Oak Park Cemetery after learning what became of his dad, and showing up just as he's in the midst of a Heroic BSoD.
Heartwarming / Back to the Future Part II