He always kept a [tea cup and saucer] up his sleeve for just such an occasion.

Note: Maybe it could be "in his hat" instead. Or maybe a birdcage hat? Fryclad and I brainstormed what might be up his sleeve (the possibilities are endless!) and here's what we came up with:

Fox

Badger

Candelabra

Bear trap

Sledgehammer

Rubber chicken

Rubber ducky

Granade

Birdcage

Tea cup and saucer