Oblechum
A person who's like a soft cookie but doesn't know how to laugh. They're nice and make people like them, but they're as funny as a wet sock.
DM: 'Hey, you're cool, but I can't stand your jokes. They're like watching paint dry.'
Tweet: 'Oblechum is the reason I still have my sanity. They're sweet, but their jokes are like a punch to the gut.'
Text: 'You're a good friend, but your jokes are like listening to a cat meow for ten minutes.'