The hashira all have animal features!! List ↓

Mitsuri - bunny ears and tail

Sanemi - folded dog ears and fluffy dog tail

Giyu - wolf ears and wolf tail

Obanai - dragon tail and dragon horns

Muichiro - leopard tail and ears

Gyomei - bear tail and bear ears

Rengoku - lion tail and lion ears

Shinobu - butterfly Antenna's and butterfly wings

Tengen - lion tail and ears