Never allow your character to be one-upped by another player's character. Or by the GM, for that matter.

Naturally, all the other players should be adhering to this principle too.

You might be generous enough to let the GM get a word in at some point. But that's not strictly necessary.

Transcript

Obi-Wan: I'm going to Utapau to track down General Grievous.
GM: His unit is only a part of the Trade Federation army. A greater force of droids is invading Naboo.
Yoda: And an even greater force is attacking my planet!
Mace Windu: They are?
Yoda: Help the Wookiees, I will.
Obi-Wan: Wookiees?
Padmé: They're kind of half-ape, half-dog, half-yeti hybrids.
R2-D2: And they're one and a half times the size you'd expect.
Yoda: Oooh, that's even better!