Keep It Stylin', Stupid

In the log book are these instructions:

If your team size is… Then…
1-10 people X+Y+Z=3
10-20 people X+Y+Z=5
20-40 people X+Y+Z=8
40-75 people X+Y+Z=15
75 or more people X+Y+Z=24

In addition, you must satisfy the following criteria:

Make an appointment with HQ. You must arrive dressed as the characters you have chosen. If we are impressed, you will receive the answer word.

The pictures themselves are available at the cache site.

Picture X:

Picture Y:

Picture Z: