1.There's a lot of setup in the beginning of the movie for Kevin's traps later on. For example, Mr. McCallister tells Kevin to pick up his Micro Machines because "Aunt Leslie stepped on one and almost broke her neck." Which, of course, is exactly what happened to Harry and Marv later in the movie.
2.Kevin's mom then tells his dad that Kevin was "in the garage again playing with the glue gun," which is a setup for the glue gun Kevin uses later in the movie to cover plastic wrap with.
3.Kevin explains he was just "making ornaments out of fishhooks." Later, we see Kevin place those ornaments on the floor under a window where, of course, poor Marv steps onto them...barefoot.
4.Apparently, everybody expects Kevin to burn the house down. When Kevin's dad reprimands him for using the glue gun, Kevin responds, "Did I burn down the joint? I don't think so." And at the end of the movie, when his family returns, Buzz tells Kevin, "It's pretty cool that you didn't burn the place down." LOL.
5.Kevin's plane ticket and passport get accidentally thrown out after the spilled milk incident, which explains why no one initially notices Kevin isn't on the flight.
6.There's a dummy of Uncle Frank sitting all alone and doing nothing in the background here.
7.It's a little hard to tell, but in order to make his ~trick~ on the Little Nero's pizza delivery guy more effective, you can see that Kevin hauled MASSIVE speakers into the kitchen.
8.The red Christmas bow that goes flying off during the storm ~magically~ reappears back on the lamp post a few seconds later.
9.Just like Kevin's dad said, the garage door is in fact left open, but WEIRDLY the cars aren’t even pulled all the way into the garage.
10.Kevin can't find his toothbrush because his mom packed it away for their trip.
11.The "robe" Kevin uses to disguise himself with in the nativity display is actually just a curtain from the display...
12.…and someone at the church apparently fixes it, because it's hanging back up again when Kevin returns later on.
13.Kevin cut out the basketball from the Michael Jordan poster in Buzz's room and had to stitch Jordan's arm together with tape...
14....although ~magically~ the poster appears altogether again, basketball and all, in Buzz's room later in the movie.
15.Several of the mannequins Kevin uses for his makeshift ~party~ can be seen in the basement earlier in the movie.
16.You can see what looks like tiny rocks (or maybe grains of salt?!) being tossed at the spider to make it move in the bathroom.
17.When Kevin's grocery bags break, the large container of Tide detergent is missing.
18.And in case you've always wondered, the bags breaking gag was achieved with string, which you can see if you look closely enough.
19.It's not easy to hear, but if you listen, the basement furnace actually says, "Hello Kevin."
20.Kevin's mac 'n' cheese dinner appears to be a totally different frozen dinner moments later when Harry enters the dining room.
21.If you're wondering why there's a doggy door in the house, but no dog ever appears in the movie, it's because the McAllisters put the dog in a kennel for the trip.
