What I do is....I always go to the Academy when I want to spar and then I call the Sim. While I'm waiting for them to arrive, I just have her meditate or something. (ya know...to prepare for the fight) Then I watch for when the sim arrives because they ALWAYS stop in the exact same spot....in the workout room right by the pole. They walk in and stand there. Then I have my sim stop what she's doing and "call over." If she doesn't know the person yet....I do the "greet" and then "challenge." If she already knows them....I just do the "challenge". Plus, this way, if you call them over, you can have your sim already on the platform ready to go and that sim will come to you and it just makes it work out better all around.