1.
Their hands are never clean.
2.
They have no respect for boundaries.
3.
They never want to sleep.
5.
When they do sleep, it's at the absolute worst possible time.
6.
They have horrible taste in television.
10.
They dress themselves terribly.
12.
They want to play with your stuff.
13.
They put food in weird places.
15.
They're freaking expensive.
18.
They're shitty travelers.
19.
They ask for help with stuff you don't know the answers to.
20.
They wake up so easily.
24.
They don't care about your credentials.
25.
They know you can't stay mad at them.