I'm referring to that security system from the movie Incredibles, the one that covered Mr. Incredible with sticky, expanding gooey spheres, slowly encasing and incapacitating him.
I'm wanting to make a similar weapon for my sci-fi riot police, a goop launcher of sorts that would behave very much like the one above.
Has anything like this been done before, and if not, is it even possible?
Thanks in advance.

A few ways you can go about this, depending on what specifically you want to accomplish.

MOPixels and MOSParticles can be instantly turned into terrain when ToSettle = true is set on them with Lua - you could form terrain to slow/encase actors.

You could also "stick" objects to the actor (Coalition grenade launcher, Dummy frag launcher) and have those objects be scripted to do something (velocity control? control input disabling?).

Hard to tell you what can be done without an exact idea on how the goo gun would be translated to CC.

Is it possible to have the projectiles stick to the actor and then start to increase in weight? Most likely with an animation to show them expanding.

Lua-based "sticky" projectiles don't actually attach to the target, they just determine their position/rotation relative to the target on "contact", and then constantly update their position/rotation to give the illusion of being stuck.

You can increase the projectile's mass after sticking, but it won't do anything to its target. You can increase the mass of the target upon "sticking" though.

Wow, I didn't actually realize that, thank you. I think i'll try the mass increase in he actor and see how it goes, I assume the effect is reversable as well.

Should be reversable, yes.

A while ago I found some strange effects occuring when trying to add/subtract mass using Lua, but I can't remember the details and don't know if those issues are still around.