This approach is common, but it is usually an effective crowd-pleaser. Dress football players or other male athletes in female clothing and instruct them to perform an activity. For example, give them clothes that resemble the cheerleaders' uniforms and let them recite school cheers to pep up the crowd or choreograph a dance for them to perform while a "girly" song plays. For a hilarious surprise, let them dress up before the rally and do not let anyone in on the secret until the event begins.
This is similar to the previous activity, only reversed. The participating girls can be cheerleaders, female athletes, members of the audience or a mixture. Dress them in bulky football uniforms and have them compete in simple challenges while in costume. The crowd will also enjoy watching the girls, dressed in male clothing, compete against the guys who are dressed in girl clothing. If enough cheerleaders and football players are dating each other, have them compete against or alongside their significant others.
A few lighthearted faculty members are usually willing to participate in embarrassing or messy stunts for the sake of school spirit. Provide the volunteers with an extra T-shirt or request that they bring their own from home to wear during the activities. Hold a contest to see which teacher or coach can find a piece of bubblegum in whipped cream pie the most quickly -- with no hands, of course. Another activity that requires a bit less cleanup is the toilet paper challenge. Gather teams of three from the audience to wrap their favorite teacher in toilet paper. The first team to fully cover their subject wins.
This activity requires help from parents. Contact the parents of a few football players a week before the pep rally. Request that they secretly loan their sons' favorite silly pajamas, blanket and childhood stuffed animal or similar toy. On the day of the pep rally, pull aside the related players and line them up in front of the crowd. Unbeknownst to them, the cheerleaders will appear shortly after, dressed in their pajamas. Ask the other students to guess which cheerleader's outfit matches each player.