The pilot has a mild Animal Motif when it comes to the characters:
Becky telling Jesse to beat it is compared by Jesse to someone kicking a fox out of a henhouse (the fox in question being Jesse, and the henhouse being the bench). However, Jesse and her posse are the ones that seem to be the actual "hens" in the metaphor; she calls her posse a "flock," their passive-aggressive nature evokes Gossipy Hens, and their rail-thin designs resemble flamingoes. Jesse also calls the bench a nest, and the carving in the back is "Prim's Perch."
Becky could be also be seen as the true metaphorical fox attacking the "hens", as she has red hair and is more aggressive. Ello is also referred to as a sheepdog by Jesse, which makes sense; Ello, at first, prevents Becky (the fox) from harming Jesse's flock (the birds). And once Ello no longer intervenes (when Becky finally gets her revenge, Ello sits quietly on the bench next to her and does nothing to stop her), Jesse's flock ends up being tortured by Becky.
Norville has one, too; a T-rex. His arms are short and he outright tries to mimic one at lunch.
Fridge Horror
By the end of the pilot, Becky has gotten her revenge on Jesse, and is sitting on the bench with Ello - right before it collapses into pieces. This leaves open two equally depressing possibilities:
Without the bench, Becky’s soul may have no reason to stick around, given that the bench was the one thing she came back for. Which means that Becky’s spirit would move into to afterlife, leaving poor Ello alone again and at the mercy of Jesse.
Alternatively, the bench being destroyed leaves Becky’s spirit restless instead, meaning that she is still stuck as a spirit, potentially doomed to haunt the school.
While it's likely just for comedic reasons, Jesse definitely comes across as mildly supernatural due to her status as an Uncanny Valley Girl, but it's made even more frightening when the episode is near its end. After Becky finishes torturing the posse, Jesse's friends are lying on the ground, completely catatonic and traumatized, demonstrating how horrifying it must have been for them. Meanwhile, Jesse herself walks it off like it was nothing more than an inconvenience. In other words, she basically walked through hell and came out the other end mildly irritated. That paired with all of her other inhuman behavior makes it clear that Jesse isn't entirely as human as she seems.
