Yeah. They're pretty much identical bar a few animation differences at most. It's blatantly the same idea. Lucas does too, but it was even more obvious they reused the assets. Coincidentally all 3 have similarities in their movesets, using even similar elements.
Incidentally, you can see some similar aesthetics between Mewtwo and Lucario, even somewhat with their jumps alone. The funny thing about Brawl's newcomers is they slightly resemble some of the cut characters a little bit. Ike pretty much has Flare Blade and a move or two of Roy. Lucario is still an energy user with very unique animations, but resembles Mewtwo's bodyshape slightly, and having a single move that's very similar(it isn't till 4 they differentiated how Shadow Ball and Aura Sphere works. In fact, the only difference besides obviously the Aura mechanic is that one shoots in a straight line. Likewise, it's kind of obvious Shadow Ball used Charge Shot to help program it. They behave very similarly in concept, but quite uniquely in execution). Wario pretty much is kind of close to Dr. Mario in the sense of the "bigger" plumber-like character, but with unique moves. Wario even is an exaggerated Mario in his moveset. Toon Link actually did reuse Young Link's assets(though it was obvious they were built from a similar mold either way). That's about it, though. The closest thing to Pichu is that a Mascot Pokemon Got In With A Unique And Poorly Designed Mechanic(Pokemon Trainer), and that's all those two have in common. I mean, technically having special weaknesses, but both I'd call a stretch. I think that's... it for somewhat similar newcomers to the cut characters from Melee.
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Anyway, it'd be neat if Waluigi could swim in the air as a forward aerial or as an actual unique move by pressing Up or something similar to Peach's Float.