Ah, You Know Him

Alice mentions Bob. Carol has an extreme reaction (usually rage or dread), or asks a very uncomplimentary question about Bob. Alice asks "Ah... so you know him?", or "Ah, you two met before", or something to this end. The variant with Carol actually running into Bob works exactly the same way - except usually it's also awkward for Bob - seems to happen less often.

Web Comics

 * Chasing the Sunset has a shopkeeper who confirms Feiht's traits... and promptly faints.
 * Exterminatus Now - apparently, for some there are "brother inquisitors"... and then there's Eastwood. "She obviously knows you well".
 * Girl Genius has Gil jumping up when Agatha mentions Tarvek... That smug condescending snake.
 * Vexxarr had a pirate bot discussing its captain. And another AI discussing its captain, of course.

Web Original

 * (The Customer is) Not Always Right: "You have been here before, sir!"