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Tear Jerker: Channel Chasers
The ending of the Channel Chasers movie where grown-up Timmy finds an old photo of himself, and the fishbowl... But he can't recognize his fairy godparents. It's more of a Bittersweet Ending, but you still almost have to hold back tears.
Timmy in the photo is crying, and the fish in the background look completely normal...
Timmy's parents' message, which Timmy finds after realizing that his parents are way better than the ones on TV (which were either not around or were complete idiots).
Future!Timmy disappearing after Vicky zaps his time-traveling belt as young!Timmy desperately pleads for him to come back.