Dead-pan

He stared for a few seconds, then asked with a dead-pan expression, “And some chiange?”

Source: wiktionary

Jimbo had seen many drifters in all his years, and they all had that dead-pan look in their eyes.

Source: wiktionary

It might be better to see the title almost as comic, in its dead-pan announcement of an Important Political Issue.

Source: wiktionary

There was his left-hand head talking and sort of yapping that silly laugh of his, dead-pan, while the right-hand head was all creased up with giggle lines.

Source: wiktionary