People can have very different reactions to some medications - if I take just one half of one Vicodin (or most rx painkillers), I feel stoned, then sleep for about 12 hours. But Vicodin gives some people energy, so, quite the opposite reaction.
From here, norco CNS side effects, which could certainly include the paranoia JLynn experienced:
Mrs Gargoyle has had many spells of waking hallucinations. She’s disarmingly casual about it, she definitely knows that they aren’t real, but they still are present in her senses. It’s just noise that she constantly has to filter out, like the neighbor’s annoying leaf-blower.
Example: “Just so you know, I am listening to you, but there are also giant hairy lobsters crawling out of the piano. What were you saying?”
I think it’s stronger, but who knows… while the compounds are similar they can affect people differently. Also you were presumably recovering from the surgery that mandated the pain meds, and that can affect your brain as well. Quite possibly the Norco wouldn’t have the same effect now (I don’t recommend experimenting with that though!!).
The only time I’ve “hallucinated” was due to medication and sleep deprivation. I actually hesitate to call it that because I was frighteningly sleep-deprived due to illness, had taken a Sonata (sleeping pill), and my mind tried to make funny pictures out of the bits of dirt on the computer screen. I knew there wasn’t really a cartoon polar bear on the computer screen, but I still remember the image :). And I learned a valuable lesson about putting the computer away when I have sleeping aids on board 
How was his hair?