The first character actor in question is Jonathan Stark, whose turn as Chris Sarandon's bullying sidekick in FRIGHT NIGHT cemented his status as one of the premiere dicks of the 80s.
Here, he's not all that villainous, per sé, but he's got this high-school bully expression plastered on his face at all times,
one that almost insinuates you're playing right into his hands with every word you say; as if the existence of everyone around him is merely an amusing set-up to a punchline he will eventually deliver.
He also gets bonus points for at one point winking and giving the air gun/'chk-chk' of approval to a chimpanzee.
The second is William Sadler (DIE HARD 2, HARD TO KILL, BILL & TED'S BOGUS JOURNEY) who is very disapproving of Matthew Broderick
and generally plays the stereotype of the unfeeling 80s scientist who would rather chase a chimp with a cattle prod than let Helen Hunt snuggle it out and teach it sign language.
William Sadler: over it.
And yeah, that's where the main issue is: this movie is not really about 80s bullies or evil scientists, it's more of a (well-intentioned) pro-animal rights fusion of E.T. and TOP GUN, but with little of the kitsch value that would imply. I didn't hate it, but even these character actor favorites and an opening song called "Shock the Monkey" by Peter Gabriel couldn't penetrate the self-serious attitude. Perhaps I'd feel differently if I'd seen this as a kid and not waited till 2014? Still: nice work, Sadler & Stark!