Characters in ensemble casts that don't really interact with each other one-on-one
TV shows usually have ensemble casts that interact with each other all of time, especially if they're all in the same friend group. But sometimes there are individual characters that even though they hang out with the whole group quite often, there are certain other individual characters they rarely if ever interact one-on-one with. As such, they don't really have a clear dynamic and it's unclear to the viewers what these characters think of each other.
For example, in Friends Chandler didn't really interact one-on-one with Rachel or Phoebe much. This was actually pointed out by Abed in Community when he was comparing to how he rarely interacted with Annie (although this would change later).
Or how in Boy Meets World, there was a clear divide between the characters introduced introduced in the first few seasons with those introduced later, which actually became a plot point in season 7. Cory rarely interacted with Jack or Rachel for instance, and Angela never interacted with Mr. Feeny.
Or how Toph never got a "life-changing field trip" with Zuko.
So what other characters in an ensemble cast rarely interacted?