No great secrets. Played around with several options and decided to keep it simple.
Stuck a long 6 gang extension lead inside and bought some remote control switches to turn devices on and off.
Most stuff is either 12v or 5v. Bought transformers off Amazon.
Tried to get something to rattle chains inside and that failed miserably so instead stuck an Amazon Echo inside and used the phone to play effects from Spotify. Easily the best thing I did.
Put a pinball knocker in to tap on the top of the lid (5v)
Put a shaker motor in (12v). It’s amazing how many young mums have decided to sit on the coffin to have photos taken. Sure there’s no connection there

Built Kevin (a vampire) using a hideous mask from Amazon and stuffed an old suit jacket. Lit from below using an led light strip from Amazon (5v)
Utterly failed to work out a way to slightly lift and drop the lid back down due to the wright of the lid. Tried an offset motor but it struggled too much. Compromised by sliding the lid down 12” to reveal Kevin at all times. In hindsight a dropping lid and little children’s fingers are probably not a good mix.
Stuck a massage pillow motor inside to make a scratching noise but kids are bloody loud at Halloween so not really worthwhile.
Getting it out is a two person job due to the weight. Turns out my daughters boyfriends tend to scare easily
We tend to have 200+ kids knock on Halloween so I must have traumatised a few.
My best set up though is still the smoking nuclear waste barrel I made. Simple to do and green leds and a smoke machine work really well.