So I've been wondering ever since Episode I: Why are the Senate boxes shaped like Frisbees?

Oh, right, I see now.

Transcript

Palpatine: Extreme Force Arm-Wrestling?
Yoda: It's like Force Arm-Wrestling.
Yoda: Only you drop the things on one another!
[SFX]: wmmm...
Palpatine: I see; like this? {throws a Senate box at Yoda}
[SFX]: Whooosh...
[SFX]: Krunch!!
Yoda: Wait, I wasn't ready!
Palpatine: Surely you're ready now? {throws another}
Yoda: I want the Wookiee pod!
Palpatine: You Jedi have always lusted after the Senate's power.
Yoda: We'd rule it better than you!
[SFX]: Krunch!!
Yoda: And I'd be... Wait... No.
Yoda: I'm not jealous of your power.
R2-D2: Don't give up on it so quickly!
Yoda: I just want to see justice done.
R2-D2: There's only one way to settle this. As an impartial robot, I'll rule the Senate.
{beat}
R2-D2: You're welcome.