These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Reportedly, while it wasn't overly large, there was a decent sized fandom for the show in Israel, of all places.
Growing the Beard: One of the only other shows besides Star Trek: The Next Generation to apply this trope literally. At the beginning, Steve Smith's beard was actually fairly short and trimmed, and as his beard grew out the quality of the show improved. Smith later Lampshaded this fact when he pointed out that you could almost tell what season a given episode was in by looking at his beard.
Heartwarming Moment: When in Duct Tape Forever Harold finally calls Red out on his constant belittling and insults, Red pulls out a photo of himself as a high schooler—and we see he was nearly identical to Harold. Red was mercilessly picked on as a kid, and he's just trying to help Harold grow a spine.
Seasonal Rot: While if and how much this occurred is up to the viewer. Steve Smith admitted in at least one interview that the show was intentionally ended to keep this from happening.
It was said outright in the last show, on screen. They were ending it while it was still funny so people had good memories of it, to prevent it becoming a Franchise Zombie.
Tear Jerker: In the last episode's advice segment, when after Red says his trademark "Remember,I'm pulling for ya. We're all in this together." line, Steve Smith gets up and has to leave the stage, because he's ready to cry.
Oh heck, the entirety of the episode is a tear jerker.