THE DIFFERENCE BETWEEN XXIV

What's the difference between:

1. St. Louis and St. Peter's?

2. Post-Civil War opportunists and what unpleasant supermarket shoppers might do at the check-out counter?

3. NASA and the EPA?

Answers:

1. The Cardinals play in one and pray in the other.
2. Carpetbaggers and carp at baggers 
3. NASA is in charge of Mission Control and the EPA is in charge of emission control.

Credits:
1. Joseph Appel 
2. Cathy Allis Millhauser 
3. Mel Rosen