Kirby gains Lucario's aura sphere. But the aure sphere follows the mechanics of normal brawl. instead of being the same every time (except when a super charge is used), it scaled in size and strength as Lucario's ability's (especially aura sphere) did in normal brawl.
I doubt that this is actually a bug, more like a mechanics issue that wasn't updated. but now it can be.
I doubt that this is actually a bug, more like a mechanics issue that wasn't updated. but now it can be.