Lacked personality in your opinion? That's actually a fact. The thing is, they huge amounts of character potential if Nintendo decided to keep them, but they didn't even get any lines in Mario & Luigi, and haven't made a legit appearence since then. As for Bowser Jr., he rightfull doesn't deserve to be in SSB as much the other Mario characters, as he hasn't done as much for the series as they have. If anything, Toad should get in before he does.