I love your take on the TTYD heroes! The Toad hero using a Koopa shell as a shield is very creative, and it fits right in with Paper Mario's funny nature. The SMB3 Hammer weapon also fits; it's a great stand-in for a sword in a Mario game.
Sine has a pretty cool design! I like how she's mostly blue and white, with hints of orange here and there. That's some nice use of complementary colors. I'd like to see Tangent, too. (Side note: I just got the pun names. Sine and Tangent... that's good. XD Is there a Cosine, too?)
I don't know anything about Lum, but that last drawing is hilarious. Not-Fred-Flintstone's expression makes it gold for me.
All in all, you did a great job! If you want to post more, I'd say go right ahead! There's no shame in posting unfinished sketches - in fact, when you submit an art piece, there's a checkbox specifically for sketches. I'm sure people will love to see it! Keep up the good work! :)