Soluciones:

THE GOLDEN CALF: Because they couldn't afford a golden cow.

WATER, WATER EVERYWHERE: None, the bottle is already full.

COOL CATS: Well, if the man has a widow, he must be dead.

A PROBLEM OF HEIGHT: By letting a bit of air out of his tyres, he manages to lower the lorry enough to pass through the tunnel.

SLEEP ON IT: Her neighbor's snoring was keeping her awake, so she rang and woke him up.

FOOTBALL: The third statement is true.

NAPOLEON: How could he hold his sword to cut off the other arm?