The word Creeper is such a fun word that describes so many different things.
First off, there's the little insects that creep around just outside your front door. They're quiet for the most part, but you can sometimes spot them because of their slight movement. Some of them fly around, then land on your arm and creep along until they hit a hair and make you look. Right now, my creepers are a hoarde of ladybugs that are looking for a place to hibernate. I have no idea how they get into the house, though I'm wondering if they're successfully squeezing through the new windows in the rooms that have lights on. I like them, but not in my house. Maybe if they each chipped in a dime towards keeping the place above freezing during the winter I'd change my tune.
Then there's a skateboard-looking device used by car mechanics. Some are quite comfy and have a head rest for when you have to slide underneath a vehicle to fix something. Others are a flat board with wheels that barely turn.
Since we covered fauna, there's also creeper vines in the flora category. These seems to grow as you watch them, figuring out ways to cling onto buildings and trees. Ivy is a good example, turning a brick fascia into a nice green living wall. Of course, there are those raspberries and strawberry ground creepers that trip you up because they grew overnight. The ones that really suck are the creepers with thorns that dig into your ankle.
Drifting more towards the bad side of things, there are so-called humans who are creepers. They spy on others, sometimes peer at underage kids with ill intent, and generally act like folks who have no social skills at all. This can be caused by things like Asperger's Syndrome, but most of the time it is people making rude comments about someone's body parts or trying to talk someone into their bed. They take advantage of people who are drinking or who are having difficulties. I once saved my wife (before we were married) from a creeper, a dude in his thirties with a 1970's van who got the hot 16 year old drunk girl into his vehicle. I bombarded his van with baked potatoes and he came storming out with his shirt off, looking for the people chucking shit at his van. She slipped off when he wasn't looking and went to get some sleep at her friend's house.
Finally, that type of van is sometimes called a creeper van. It can be owned by a creeper, or it can be like my Ford Transit Connect, a cargo van with no windows. I use mine to transport my books to conventions, but we still call it the Creeper.
Nemosyn says re Creeper: you forgot the Minecraft creeper. They are green, rectangular, and kind of cute. They are also the most likely use of the word creeper.
Iron Noder 2017