Odd question, feedback welcome...

If someone says something like "You're such a creeper" or "Hang out like a creeper" do you take it as a joke or as something offensive? I ask because this has always been a funny silly thing among me and friends/siblings and I think my T thinks its an offensive statement was very confused about it, we had a weird discussion but I didn't know how to really explain it after a bit. Maybe I'm in the wrong?