Overanalysis: A Hypothetical Predator in Action

I came up with an idea for how a predatory version of a certain purple dinosaur could work.

First of all, Barney takes the form of a therapod dinosaur (2 legged carnivores including raptors and T-Rex), presumably a tyrannosaur himself. This implies his diet is carnivorous. This presents a problem: Walking down the street as a hungry dinosaur means he's likely to draw unwanted attention. So transformation/hibernation in a "harmless" state is a good survival tactic. That's why he turns into a stuffed animal.

Barney obviously wants to avoid adult attention. Adults, even those not knowing that they're facing, are still stronger, more experienced, and more intelligent than children are. Like other predators, Barney prefers weaker prey: children in this case. That's why he adopts the purple and green look as friendly humanoid dinosaur. He primarily transforms into this state in the absence of adults, and does little other than try to befriend children. He essentially uses a charm predator strategy, luring in and distracting prey to isolate them.

Now, Barney's humanoid form is obviously his primary hunting one. His head has jaws clearly big enough to devour children or swallow them whole, and he only takes that form when he's certain no adults are around. Barney also probably has little issue cleaning up after each victim, given he can clean himself each time he shapeshifts and has a magic bag he can easily hide or transmute any leftovers in (or perhaps souvenirs from previous victims, fetishistic totems similar to those taken by serial killers).

The lineup of children changes every few episodes, and this could be clear evidence of this tactic. It also implies that Barney convinces his victims to bring friends to replace those who have been eaten. Barney's always trying to reassure kids, hence the song and dance routine. Cult leaders, kidnappers, and creepy fellows in the back of vans often try the same tactic. He might also have some kind of supernatural hypnosis, mental suggestion, fey-styled glamor, or mind control, given he's always got a full group of "livestock." It also suggests there are limits to how many people he can control or influence at once, or he prefers smaller groups that are easier to isolate and manipulate. So, a stupid children's show just got a whole lot darker, thanks to overthinking it.