Honestly, there's not much that Tony could do in terms of body language that could disturb Bruce. He's used to the intensity with which Tony studies anything and anyone that catches his eye until something else pulls him away like a hummingbird whose feeder had been filled with Jolt instead of sugar water.

"Underoos?" He's nonplussed because there's zero context there but it doesn't sound good. "Splooge?"

And now there's nothing for it but to watch this skinny figure brachiating (it's the closest verb he can think of) around New York on-- "What is that fiber he's using?"

Now he sees where "Underoos" comes from, and splooge is starting to make sense, too. "Who is this guy?"