The ending of "Dream Hoarders". Jimmy is adamant that they can't continue with irresponsible behaviors like wasting money on lotto's and Virginia storing random (and dangerous) junk for a house they will never have. Jimmy has a point, but after talking with Sabrina he realizes his parents were always dreaming of something better, and relents on those actions.
The reason behind Burt's actions in "Happy Halloween". He loves his son and is saddened that Jimmy doesn't hug him anymore.
Jimmy: Even though I was a mistake, I'm a mistake my parents would gladly make again. And that is something you and I definitely have in common. I couldn't have planned how you came to me in a million years, but I always want you to know that you're the best thing that has ever happened to me.
The revelation at the end of "Don't Vote for this Episode" that the Chances aren't abusing Maw-Maw's dementia for a free house. They actually proved themselves capable of living on their own, but when Maw-Maw started having problems, they swallowed their pride and moved back in to take care of her.
In addition, everyone yelling "Surprise!" every time Maw-Maw forgets it's her birthday party.
Maw-Maw: Oh my goodness! For me?
In "Sabrina Has Money", when Sabrina apologizes to all of her friends for lashing out at them due to insecurity issues, and Virgina returns the 2000 dollar gift toilet and 100 dollar lobster after getting carried away with fantasies about a rich life.
Burt "stealing" the perfect wedding for Virginia.
Burt's father calling Burt "a better man than me" for being able to deal with living a working-class life in order to support his own family.
The whole last 5 minutes of "Jimmy's Fake Girlfriend" with Jimmy writing a play for an improv group to show Sabrina how he's always loved her.
A minor one: In "Spanks Butt, No Spanks" Sabrina comes into the kitchen in the morning, the first thing she does is hug and kiss Hope, like a mommy would.
In the season 3 premiere, when Jimmy takes the chance (no pun intended) of ruining his relationship with Sabrina, just to tell her the truth. And she still accepts his marriage proposal.
The Chance's call in Barney to babysit Maw Maw while they're off at a couple's retreat. Right after they leave, he calls his mothers and has to call off his birthday brunch tomorrow because he thought being called over to watch Maw Maw was an excuse to get him to a surprise party. Over the episode Barney and Maw Maw bond, and it's quite touching how she tries to help him celebrate (not to mention hilarious when, after he passes out, she puts him in her bed and lets him come to conclusions the morning after). When the Chances all come back, they see Barney acting odd and leaving. After Maw Maw explains, Jimmy anxiously asks her if she told him about the big surprise party they've all set up for that night. She says of course not.
In "Squeak Means Squeak" Sabrina is challenged by Jimmy to take care of Hope for a weekend and not pass her off once the fun stuff was over. Sabrina was confident she could because Hope listened to her better than to Jimmy, but after that weekend has a minor breakdown over how much of a handful she can be, because now Hope doesn't listen to her. She finds out why when Hope calls her "Mommy". Sabrina's near Tears of Joy when hearing this, then hugging Hope afterwards just sells this moment.
Jimmy's narration during this moment is also very sweet, as he explains the trade-off that comes when a child knows you love them unconditionally.
Burt and Virginia doing everything they can to make sure Jimmy and Sabrina's wedding goes perfectly. It does, and few know how close it came to disaster.
At the end of the episode, Sabrina has a message for Jimmy on their wedding video. She knows Jimmy thinks he's so lucky to have HER, but she says SHE is the lucky one to have him, and Hope, and all his family. We're not sure if they got everything, as Burt was trying to destroy all the evidence that Lucy was alive and came to the wedding to kill Sabrina.
"Arbor Daze": The montage of Burt and Virginia going all out to celebrate all the holidays they could, just for little Jimmy.
Almost the entirety of "Mother's Day." Virginia was jealous that Sabrina gets Mother's Day rights from Hope, while she spent the first few years raising her (much like how she considers Maw Maw, her grandmother, to be her mother). Seeing how much it hurts her, Sabrina decides to pass Mother's Day rights from her own mom to Virginia, explaining that she has been more of a mom to her despite not actually having the title. While it involved a little deception to make her feel better (recruiting Frank and Shelley to fake a phone call) the last words has Sabrina saying "I'm with my family."
After her narcissistic gay father leaves again, the Chances and friends watch home videos of the real father figure Virginia had. Papa Wilfred.
Pretty much all of the "re-birthing" in "Adoption." Jimmy senses that Sabrina is uncomfortable with questions regarding her not being Hope's biological mother, even after officially adopting her she feels unfulfilled. The actual "re-birthing" is rather silly (and ends with an emergency c-section performed by Sabrina herself) but the gesture from Jimmy and the affection Hope gives her afterward brings her to tears.
From the series finale, the Call Back to the Pilot when Kenny Loggins sings "Danny's Song" at Burt & Virginia's wedding. Also when there's a flashback of Virginia singing the song in the Pilot.
The way the whole story was brought full circle with Virginia's dad coming to stay with them and mend his relationship with her. Jimmy says it all, "You don't always become a parent at the perfect time." and no one on the show had a fairy tale experience, but that doesn't mean they aren't a loving family.