What do you imagine tagging around in a pocket would be like?
Just kind of spitballing about this one and probably not going to be able to edit it too well before posting, so apologies in advance for the rambling!
In short: Depends on the pocket!
In long: Anything waist-level or lower and you're dealing with a lot of movement (depending on how tight the clothing is, as well. Pants pockets? Terrible, never, but the lower pocket on decently-long coat? Yeah that could be do-able.) but a lot of the time I tend to focus on chest pockets.
Chest pockets make communication way easier for the smaller person, could be tight and very warm in there depending on the chest/clothing makeup. I've always kind of imagined it like a very deep hammock sort of situation? You can stand in it but it wouldn't be tremendously stable.
The lower pockets (or even like a hoodie pocket, but god that would have to be just... so warm) allow for more opportunities for subtle touch/holding with the big's hand(s). Communication gets harder outside of that, but if you're just tagging along for fun, then it's not a bad sacrifice. (Possible solutions involve cellphone earbuds and the like).
Lint and dust are always one of those logistical thoughts I try to throw aside for the fantasy of pocket rides.
On the topic of logistics: movement could be intense. I am someone who, especially during the work day, am doing a lot of moving and rocking back and forth around my workstation, my hands and arms are always busy, and I will often take several steps backwards or spin/dip to get things/do things. If you can't see what's happening outside of the pocket to perhaps give you warning or at least context to the movements, I could see anyone with motion sickness issues (or even people who don't normally have an issue with that!) being made pretty uncomfortable throughout that sort of thing. If the fabric of the clothing is slack compared to the person's body, that's a whole additional level of swinging that could be added as well.
You've also got to worry about positioning of the pockets for things like: possible collisions with the environment/other people, what's going to happen if the person sits down/stands up, how much of a noticeable impact is the tiny making in that pocket, how hard is it to get the tiny in and out of that pocket and so on.
Thank you so much for the ask!