You just have to make Jimmy a grappler.
I'm not sure which frequency determines the grapple reversal yet (since I can't be bothered to go through all these numbers)...but if you just want to see it in action, swap Jimmy's stats with a school clique grappler, or a dropout striker and change Jimmy's main stat to STAT_BOSS_RUSSELL (if you were to replace your stats with a greaser grappler, you'd change G_GRAPPLER_A to STAT_BOSS_RUSSELL).
All you have to do then is let a Jock or Townie attempt a knee drop on you.
