Oklahoma State has a line in two of their songs where it officially says "(opponent)", but their fans yell "OU", even when they don't play Oklahoma.

Ride, ride, ride, ride,
Ride ‘em Cowboys,
Right down the field;
Fight! Fight! Fight! Fight!
Fight ‘em Cowboys, and never yield.
Ride, ride, ride, ride,
Ride on, Cowboys, to victory;
Cross (opponent)’s goal;
Then we’ll sing “O-kla-homa State!”

GO! GO! GO POKES! GO POKES! GO POKES GO!
O!…S!…U!
O S U
The greatest in the nation
O S U
The team that’s got the go spirit and the will to win
Make a score and we’ll shout
Beat (opponent)!!
O S U
It’s orange and black we’re cheering on to victory today
And then we’ll say
O-K-L-A-H-O-M-A!
STATE!
Univer-si-ty!