Creative prompt:

Alright writer, that sounds like quite the doozy of a problem! This is what I would do in your shoes. These crabs sound like they like to joke around, right? Little practical jokes, mostly harmless, pinching your nose and such. They're having a laugh. You want them to leave? You gotta up the ante and show them you have some jokes up your sleeves as well. But dark jokes. Jokes that aren't really jokes. Get a pot of water and place it outside of your car. Have them watch as you set the pot to a boil. Go and find a few of their little crab friends that were wandering around and bring them to the pot of boiling water. Look the crabs in your car in the eyes and smile. Crack some jokes for these jokesters. 

"how does a crab feel when it's dropped in a pot of boiling water? Clawful!"

"what does a crab use to call the police when it sees their buddies being dropped into a pot of boiling water? a shellphone!"

"hey, lads! lets all clam down, shall we??"

hopefully they realize the severity of the situation when you grab the butter and make their way out of your vehicle on short notice. Hope this helps!