That, Plus the Lab Test

Nerdy chick picking dirt off shoe with fingernail: I wonder how I got all this mud on my shoe...
Nerdy boyfriend: That's not mud; that's dog shit.
Nerdy chick, horrified: How do you know?!
Nerdy boyfriend: I saw you step in it on our way over here.

--Great Lawn, Central Park

Overheard by: Big Larry