Ally Adjacent

Right out of my homegame, there’s my party’s rogue attacking a giant purple worm and dealing bonus damage because the druid is currently making their way through its gastrointestinal system. A quirk of the rules in 5e compared to 4e and 3e since the ally just needs to be “within 5 feet” and working ones way through a creature’s digestive system is notably less than five feet away. Arguably, it’s zero feet away.

I suppose if I was trying to swallow something that was fighting back and attacking me from the inside, I might leave myself vulnerable to an attack as well.