Jesse and Yumyulack's relationship in general. While they do bicker and sometimes engage in dangerous Sibling Rivalry, Yumyulack makes it clear that only he can terrorize Jesse. Everyone else will either get shrunk, shot, or blackmailed. Jesse will also turn to him for advice if she's desperate.
Korvo and Terry aren't officially romantic partners, but they act like it. The two also bicker, but Terry has admitted he likes Korvo for being a smart stick-in-the-mud after a few weeks of him acting like a ditz.
Pupa is supposed to be evil, and a walking tyke bomb for the apocalypse. He also spends a portion of his subplots befriending animals or people.
Pupa freeing a bunch of animals (dressed like fictional characters) from an auction.
When Korvo 'dies' during a magician act, the rest of the characters are genuinely heartbroken. They are also relieved when it turns out that he is still alive.
Terry and Korvo letting go of Funbucket.
In "The PATRICIA Device", it appears that Terry and Korvo have made a human friend, who is willing to show them around his man cave. In fact, the episode, in general, shows people being more accepting of the aliens.
Even though Molly's owner is annoyed at Yumyulack for shrinking him and locking him behind the wall, he considers it the best thing that ever happened to him, as it led to him meeting her.
The season opener
Korvo realizes that he can't give up the Pupa to the other Schlorpians on learning that Jesse and Terry need his help. He busts himself out of the cage they lock him into, and comes to resolve the conflict. Korvo gives Pupa another gun and orders him to defend himself, before grabbing Jesse's new dog and presenting it as the Pupa. He can be a Papa Wolf when the occasion calls for it.
It first is cruel of the "cool kids" to lie to Yumyulack and ordering him to have a sleepover so he won't find out about their real party. When they toss him into the trees, he comes back in a rage and prepares to murder them with a satellite. Before he can do it, a boy named Darryl shows up. He asks if the sleepover is still on as scheduled, and finds Yumyulack's human wall of adults cool. Yumyulack abandons the murderous intent and invites him to dinner.
In a black comedy sort of ways, Terry (whose snapped mentally due to Korvo changes in the timeline) finding peace and solace later on in his life.
The Solar Opposites show genuine guilt and remorse when they truly believe that they tortured Peter and they willingly accept their Fate Worse than Death punishment. Ironically this is one of the few times where they actually did nothing wrong and were framed.