Tear Jerker / Sonic Underground

  • The song "Someday", where Sonic vows that someday he will unite with his siblings.
  • The triplets' adoptive parents being roboticized, and almost every time they ran across Queen Aleena.
  • Sonia seeing her adoptive mother as a robot.
  • Cyrus's father being roboticized. The episode ends on a sad note as he silently throws pebbles into a pond.
  • "Let the Children Light the Way," although it might be Tastes Like Diabetes for some.
  • In "Mobodoon," Manic feels like he belongs in the idyllic Mobodoon, but staying would mean he'd have to leave his siblings behind—and he realizes his real home is with them.
  • After 10 years of being Cut Short, it seemed that the story would conclude in the Archie Sonic Comic's Sonic Universe. Sadly, it was delayed, and now it's been officially cancelled, though a summary of its events will appear in a collection of planned and scrapped stories.
  • The demise of Hip, the robotic baby hedgehog: Hip was a surveillance robot built by Robotnik to trick the SU into finding Sanctuary, a freedom fighter orphanage. Manic had grown fond of Hip, thinking it was a real baby. When a fight led to Hip falling from high in mid-air, Manic tried desperately to save the robot, only to fail as it smashed into the ground, revealing the truth. You honestly can't say for sure what was harder for Manic to process: the Robotic Reveal or that he watched helplessly as a baby he cherished died right in front of him. Even worse, there was an indication that Hip had become sentient, as it dreamed of playing drums with Manic.

http://tvtropes.org/pmwiki/pmwiki.php/TearJerker/SonicUnderground