Any Smunch-sized space will do
As you can see, Rimonit is thrilled to have dumped out whatever was in the basket under her stroller seat in order to make room for her to climb into it. If I recall correctly (this is from about a month ago - okay okay, we take too long to upload our photos), this was the same day or the day after she had snuck one of my shoes and one of Warren's shoes into the basket as we were about to leave for day care; and if shoes can fit inside, why not a Smunch?
She now channels her stroller-related climbing ability into clambering in and out of her regular seat, which she does all the time now, requiring us to keep the brakes on in the house so it doesn't move around while she climbs (it's a stable stroller, so fortunately we don't have to worry about tipping-over issues). All in all, she's quite the monkey.