Well, it started when a friend of mine started sharing a few FiM pics/comics and I showed him this comic I had just found on Equestria Daily (posted below) -
Considering I am completely obsessed with Applejack, I told my friend that I had just found the perfect ship in the fandom. My friend then joked that I should find the other me to complete the ship, and posted a link to one of their friends whose username also had a variant of Applejack in their Steam ID shortly after. I immediately responded by saying all I needed now was...a jar of peanut butter. It took my friend a few seconds to register what exactly I was implying, but when he did, his reaction was hilarious.
So yeah, I've been annoying him with the whole peanut thing ever since. XD
PS - I choose peanut butter because peanut butter goes great with celery and apples and thought it would be fitting for a naughty joke.