If I put something from another game in one of my mods I’d do it in a joking way and wouldn’t make it serious at all.
In my last mod you kill Nasher after insulting him for being a greedy horrible $£^*!@… The name was changed ( slightly ) to protect the guilty but he had the same head. Yes, that was done for personal satisfaction.
“That’s one doomed space marine.”
Yeah, easter eggs have generally been OK, stuff from other games can be a little cagier.
Awesome, thanks. It is a risk of breaking immersion too. I’ll avoid the temptation 
I should say, an easter egg doesn’t have to be a humourous thing, but a little tidbit hidden away and not made part of the main attraction. Something done in passing you have to kind of find. There’s a few of these in NWN 1, can’t say I know of any in 2, done mostly through references in books.
At least for me, easter eggs are more satisfying if I have to put in some effort to find them. I am always happier with implied connections to the thing. Or maybe needing to be off the beaten path to notice something.