The light is on but nobody is home 

A common phrase used to refer to someone who's perception is very, very slow. An imbacil for example. Someone who just can't understand.

A: Excuse me, what time is it?
B: Time for you to go home and play with soap!
A: But my mom will be angry if I waste soap?!
B: The light is on but nobody is home
C: Kalevet!!!

The light is on but nobody is home by wandman September 1, 2005

The lights are on, but nobody's home 

1. Literally, when someone leaves their house and forgets to turn off their lights.
2. Joe Biden

1.
John: hey, let's go across the street and drop in on Bob.
Jim: I don't think he's home right now.
John: but his lights are on
Jim: yeah, but I saw him leave a while ago, he must've forgot to turn off his lights when he left again, he does that a lot.
John: damn, I was really looking forward to having a few beers and some great conversation with him!

2. Joe Biden is literally the definition of 'the lights are on, but nobody's home.' I mean he has a brain, (or wait does he?), I mean at least I think he has a brain, but we never see it used and it doesn't work properly most of the time, he's alive and here physically but mentally he's dead and gone.

The lights are on, but nobody's home by Cornpop was a bad dude July 20, 2022

why is nobody talking about the warning we get when we follow you 

When someone wants followers and gets their friend to comment on their post to fool the ignorant

James: hey dude, I need followers. can you tell people they’ll get a warning when they follow me?

Nathan: sure bro

Nathan: why is nobody talking about the warning we get when we follow you?

why is nobody talking about the warning we get when we follow you by Your uncle’s friend’s sister November 13, 2022

Nobody said you had to supply the sound effects! 

What an annoyed attendee snorts at you when you sarcastically voice a gross/crude/embarrassing "audio clip" during/after a humiliating event that others would prefer to hush up or forget/ignore.

Wry-faced storyteller: "...but needless to say, that big plate of beans very decidedly did **not** completely agree with me, and so I ---"
You: "July is National Baked Bean Month --- ppppppprrrrrrrppppppffffhh --- excuse me!"
Wry-faced storyteller, casting an irritated glance in your direction: "Hey --- that's quite enough --- nobody said you had to supply the sound effects!"

Nobody said you had to supply the sound effects! by QuacksO June 12, 2018

the somebodies of yesterday are the nobodies of today

most celebrity athletes, entertainers, personalities, politicians who achieved the bulk of their success the other side of the millennium (i.e., the 20th Century).

Think about it. How many late 20th Century celebrities are still in the public eye today ? Not many, right ? The somebodies of yesterday are the nobodies of today ...

the somebodies of yesterday are the nobodies of today by Virgin Suicides September 27, 2017