Schtitt and Mario hang out (p. 83)
They respectively walked and tottered, ice-cream-bound, Mario moving like the one of them who was truly old, mind off his stride because he was trying to think hard about what Schtitt believed. Mario’s thinking-hard expression resembles what for another person would be the sort of comically distorted face made to amuse an infant.
Context
The paired-gait formula — the near-seventy coach walks, the eighteen-year-old totters "like the one of them who was truly old" — and the thinking-face rendered comic without a gram of cruelty: the register the whole Mario thread is built in.