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Tear Jerker: Sonic SatAM
The Sonic Sat AM cartoon, the serious one, had several about Uncle Chuck, such as the end of Sonic Conversion, where he has his free will permanently, but still has to stay in Robotropolis.
The ending to "Spyhog". when the others learn that Uncle Chuck is staying in Robotropolis. He refuses to argue, telling them to "Get those long faces back to Knothole. I have work to do!" Then, after Sonic leaves, he hugs Bunny and Sally and tells them to take good care of his nephew. *sniff* Ocular Gushers to the max.
What about one of the earliest episodes, "Ultra Sonic", when they first find him and can only temporarily restore his free will with a power ring? Who could forget Sonic deperately begging his uncle to snap out of it, ignoring his friends' pleas to hurry, Bunnie having to pull him away in tears, and the poor kid crying as they flee for home?
Especially given that at the time, Sonic hadn't seen Uncle Chuck for ten years.
This Yank the Dog's Chain was almost mirrored with Sally in "The Void", after finally reuniting with her father and escaping with him out of the aforementioned portal, they discover his body is dying and turning into crystal without the Void's magic and he has no choice but to return. King Acorn kisses his tearful daughter on the forehead and asks Sonic to take care of her before he is dragged into the portal. Later, back in Knothole, Sonic is left to comfort Sally, still in tears over her loss.
"Sonic Conversion" has this in spades.
Bunnie's tears when her body, which had finally been turned back to flesh and blood, suddenly reverts to its cyborg form.
Tails's terrified begging as he and Antoine are taken to Robotnic's lair by the newly-reverted Uncle Chuck.
"Please Uncle Chuck! I don't want a robot! Let us go!"
Uncle Chuck being forced to stay behind in Robotropolis yet again, having only just fought off his robot slave programming.
Any time Uncle Chuck shows up, expect it to all end in tears.
"Blast To The Past part 2" has several, back to back.
Sally's reunion with her father. Happy tears all around.
Sally: Your Majesty... (softly) Daddy...it's me.
King Acorn: (annoyed) Sir Charles?
Uncle Chuck: This will be hard to believe, Your Majesty, but she's come from...the future.
King Acorn: (skeptical) The future? (glances back at Sally, looking deep into her eyes) Sally...?
Sally: Yes, Daddy.
King Acorn: (kneels, taking her hand) The royal signet! (whispers) What is our secret family credo?
Sally: (whispers back) To rule with honor.
King Acorn: Sally, it is you!
(They embrace tearfully.)
Young Sonic watching Uncle Chuck being roboticized. Poor kid.
Sally's desperate final exchange with her childhood governess, Rosie (who in original history was capture and roboticized when Sally was just a child).
Rosie: I know it's you, princess. You can't fool your old nanny!
Sally: Rosie, I have to tell you something—
Sonic: Bots coming!
Sally: I can't explain now. Just promise me you'll never leave Knothole!
Rosie: Never? Dear, I-I don'tó
Sally: Please, Rosie! It's very, very important!
Rosie: Well...all right, then. I promise.
(They embrace before Rosie escapes through the tunnel.)
Seeing the destruction of Mobius firsthand, especially the banishment of Sally's father. Really drives home how much of a monster Robotnik is.