There are two of something???
Dueling dragons - 2 Dragons/coaster
BTTF - 2 Deloreans
Dr. Doom - 2 drop towers
E.T. - 2.. um.. ETs (one in the bike basket, then another, um, at the end when he says your name??)
HULK - 2... er... I thought I could come up with an example by this point... I thought wrong...
WAIT! Is it the number of seats???
Each ride has four seats to a row?
-Kevin