Punk Rockers to Change Lightbulb

Q: How many punk rockers does it take to change a light bulb?
A: Two: One to screw in the bulb and the other to smash the old one on his forehead.

Light Bulbs to Change Light Bulbs

Q: How many light bulbs does it take to change a light bulb?
A: Two, the new one and the old one

Light Bulb - Graduate Students

Q: How many graduate students does it take to screw in a light bulb?
A: It all depends on the size of the grant.