the situation arising from a desire to invite one friend to an event which results in a social obligation to invite a large number of additional friends to said event
Inviting Smiley Sue means you have to invite Laughing Lisa, which then leads to inviting Debbie Downer. And if you invite Debbie Downer, you need to invite Smelly Steve. And so on and so on....
Example: "I would love to invite you to my party, Smiley Sue, but doing so would inevitably lead to a friendalanche."