A blonde...

...works in a petrol station filling up cars. One day, a spaceship with 'UFO' written on the side lands next to the blonde. The blonde cheerfully fills it with fuel and the spaceship flied off.

The blonde's boss, shocked, comes out to ask why she filled it up.

"Do you know what 'UFO' stands for?" He asks.

"Of course." She replies, "Unleaded Fuel Only".

credits to u/Mr-Everest