I've brought breathing "stuffies" in too.

Itty (a cat) used to come with me before she passed
Grace (dog) has come with me
And DC came once but he kept trying to pee behind T's couch so he hasn't been back (I had brought a travel litter box but he was having a 'guy' moment). Most embarrassing session EVER!
Omi used to come to old T but she seems to be under a lot of stress so I don't make her do the service cat thing any more.

I would definitely bring Jazzy (my pony) to session every week if I could! there is a nice small grassy spot out back... Jazzy has big shoulders to cry on and T is a horse person!
But as funny as it was to think of a car driving down the road to T with a giant bee in it I don't think mine would even fit. 1,200lb of legless draft horse in an old cavalier! I do think she would like to stick her head out the window like a dog though and pretend she was running really fast