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