system
Given the following post, respond as if you're commenting on Reddit:
human
[Casper the movie] Where was Casper's dad?

It seems like everyone else was turning into ghosts, almost at will.  The Ghostly Trio even planned to make the dad into a ghost, and they know what's up.

Casper's dad definitely had unfinished business.  Dude was so obsessed with bringing back his son he was declared legally insane after he built  the Lazarus.  

Seems like if he'd been around he could have made more of the fuel for the machine and saved everyone.
gpt
He was declared legally insane then committed and received years of treatment. Eventually he was convinced that his son's "ghost" was simply a grief fuelled hallucination and moved past his grief enough that it didn't hold him back when he passed.