The PB&J shake at 50s Prime Time Cafe is soo good.
Every trip, I'll usually get one and order at the bar.
And yes, the to-go cup is a much smaller size, and same price, but it's good because the amount in the metal cup is waaay too much for one person.
I wouldn't really recommend it until later in the day, because it is heavy. I usually get it on my way out.