It starts with the interior of Homer's garage. He drives his car in and hits one of the shelf supports.
He gets out of the car unaware that a heavy power tool is sliding down toward him.
BONK! It hits him on the head!
After a beat (above) he continues walking, looking like a zombie.
Inside the house he walks matter of factly into the bedroom...
...gets into bed...
...and immediately falls asleep.
A moment later his alarm rings. He turns it off thinking it's morning.
He gets out of bed to go to work, and begins to walk O.S.
Now we're in the living room, on the second clip. Without warning a door opens and Homer comes in, causing skateboarding Bart to smash into the door.
Homer takes out an invitation to a barbecue, and hands it to his daughter. Squashed Bart is behind the door.
I could go on, but there's no more space. Do you see why I like this transition? He's still effected by the hit on the head. When we see him leave the bedroom we expect to see him making breakfast in preparation for going to work. We think that's the gag, that he didn't get any sleep. Instead we see him in a happy but still ditsy state announcing to his daughter a cock-eyed invitation to a barbecue. It's so unexpected.
I love board gags that lead the audience to expect one gag, then hits them with another.
Neat, huh?
[BTW: Some of my offline friends disagreed with me and said they couldn't see anything of value in the post above. Haw! De gustibus non disputibus (There's no disputing taste)!]