Feats for sharing the same square

[Blue_Sky]

Does such a thing exist? I know it's a weird question. However, I've got an idea involving twin summoner stuff, and was wondering if there were ways to make the above work. All I need is for two characters to be able to share the same space.

[Danny StarDust]

Ratfolk can, with their race trait "Swarming"

[Scott Wilhelm]

There is a Swashbuckler Archetype, the Mouser, that can.

There is a Style Feat, Monkey Style. The Monkey Shines Feat allows you to enter an Opponent's Square.

Any creature that is size Tiny or smaller can enter an opponent's square.

[avr]

Vexing dodger rogues can climb a creature at least one size larger than them too, and swarm shifters can turn into something enough like a swarm to share the space of other creatures.