Alright, I got all the shots for Mario and Luigi, and I even found some new cameos!
(Dunno if it's cool that I'm posting these here XP)
Download01 is nothing special, but maybe someone could find something important in those symbols?
05 is Popple saying "I'll remember this, which is what Birdo says when you beat her in Super Mario Advance. Birdo and Popple eventually become "a couple" in this game.
06, 07, and 08 are from a book in Beanbean Castle Town that makes mention of the Gamecube controller. I think it's just mentioning that if you play this game on your Gamecube, you can find hidden items...
09 is a ghost from Luigi's Mansion. Whenever these ghosts appear, they only bother Luigi and chase him around.
22 is also nothing in particular, but this painting only appears in this area of Hoohoo Hooniversity (as well as some battles) so maybe it's an inside joke? Who knows.
24 is a part of the barrel jumping minigame. Luigi seems to take the place of Pauline when he yells "Heeeallp!!"
25 are just crabs. But given the cameo in 49, I think they were meant to be Sidesteppers.
26 is the Toad Express. The plane from Super Mario Sunshine.
27 and 28 show Luigi with the Poltergust, another reference to Luigi's Mansion.
29 shows the Super Poltergust 3001 which is rideable. This could be a lead in the the Poltergust 4000 which Luigi rode in Mario Kart DS.
32 is the arcade with the D-pad A-B scheme on top. I looked all over to a reference to WIN-tendo (as you have listed on the site) but I couldn't find it
34 and 35 is the Koopa Clown Car.
36 and 37 show a flagpole outside of the hospital in Little Fungitown. If Luigi (or Mario later in the game) jumps on it, he slides to the bottom and then jumps off.
40 and 41 is just Luigi being gay XD
49 is a Sidestepper that will randomly appear during the battle with Hermie.
50 and 51 show Boddle turning into an egg and performing the throw move (with himself) from Yoshi's Island.
53 is a secret cave. In these caves, whenever you touch something the death music from Super Mario Bros. plays (in 8-bit) and your character falls off the screen.
54 and 55 is just a character that looks like Petey Piranha.
57 is during the battle with Popple and Birdo. If you beat Popple first, Birdo says "That's as far as you go!" which is also what she says in Super Mario Advance.
The Koopalings' intros reflect their personality and sometimes how they were fought in previous Mario games. Iggy is shown to be hyperactive (especially in New Super Mario Bros.) so what he does is spin around the Bros. super fast to make them dizzy (59 and 60). When Morton was fought in past games, he would climb up the ceiling and jump down. Here he does the same but also creates shockwaves (61). In Super Mario World, Lemmy would hide in a pipe and sometimes a fake would pop out while he attacks. Here he creates three fakes and you have to find the right one (63). Whenever Ludwig had been fought, he would slide around in his spiked shell. Here he does the same and so Mario and Luigi have to make timed jumps to dodge him (65). Roy would also jump up and try to stomp on the Bros. He was also in charge of the sky in Super Mario Bros 3. Before you fight him here, he jumps up into the air for quite some time, then lands on the Bros. because they think he left (70). In Super Mario World, Wendy would pop out of random warp pipes. Here she does the same and you have to whack her with a hammer (71). Strangely enough, Larry is the only one who I can't figure out. He hits a fireball to a Bob-Omb with a tennis racket, trying to blow up Luigi...unless that's the same racket Bowser uses in Mario Tennis...I don't see anything stand-out here (72). Additionally the battle order is the same as Super Mario World.
64 is the Mecha-Koopa from Super Mario World.
66, 67, 68, and 69 is an area in Bowser's Castle where Mario crosses a bridge and jumps on the axe. Then the bridge disappears and the fake Bowser is dropped in the lava.
73 appears to be taken from the ending of Super Mario Sunshine but with Luigi added.
