When someone says they're picking someone's teeth, they're changing their mouth to get you to say something that they want you to, usually for a setup or to make them mad.
Sorry I have to study for a couple of hours.
Sounds like a lot of fun! Are you having fun?
No??
Haha yeah I'm just picking your teeth.
A trip to a grocery store, convenience store, or gas station for the sole purpose of buying an excessive amount of junk food and sugary drinks, usually with friends. A chud run often happens late at night and ends with everyone involved hating themselves afterwards.