1. it looks like 'rip'.
2. it's unoriginal. in a sucky way. unoriginal can be cool. like 'yo dude' or 'wtf'.
3. it's written on spooky halloween tombstone cookies. and it's said to dead people. how moving.
4. it means nothing. the person is dead. not resting. you should say 'RIP' when someone's about to take a nap.
5. it's supposed to be compassionate. but it's more like 'i acknowledge you're dead'.
HOWEVER, it is funny when it's in reference to a recently destroyed sandwich.