So its all about H_R now, Aye Kirin >_>
IMO the matchup is even, or slightly in either characters favor.
Toon link has his projectiles, Mario has his cape.
Both characters like to combo, Mario more so.
Most Toon links will camp if they're not famliar with the matchup, The Cape and shield will make that a bad option.
Mix up your porjectile game so that mario can't read you like a book and reject every projectile.
I usually arrow cancel at ever possible oppurtunity, later on in the match, A good player will catch on and cape nearly every arrow, so mix it up.
Use more bombs than usual, cape won't really do much to them as long as your not standing in Mario's face.
At low percents you'll find yourself in alot of u-tilt combos leading into Nairs or Uairs if your not careful.
If your d-throw'd, expect a uair or two and dodge it.
Fireballs move slowly, and oddly enough this can make them very annoying to deal with. From a distance, Mario may use a fireball and run after it. Do NOT be hit by the fireball, the hitstun will allow Mario to follow up with whatever he wants (Lol hitstun in brawl.) But this won't happen often.
Mario kills far earlier than Toon link, so save your usmash till about 110-120 and get campy when your damage is starting to get high.
His Bthrow isn't as powerful as Ness', But its still something you should be aware of.
Mario's nair has great priority , space your zair and other arieals and be aware of it at all time.
Mario's Bair and Uair are just as much of an issue, though it shouldn't happen, you may find yourself being hit by bair several times in a row, same with uair.
Poke with zair if your finding it difficult to not be hit in the air, don't follow up unless your sure it will hit.
Both characters can gimp eachother.
Mario's recovery isn't great and a well placed fair or nair can gimp him when offstage.
If you didn't knock him far enough away, don't bother stalling with the tether invincivibilty, mario will stall with his cape and you'll find yourself in a bad position when knocked off the ledge.
Mario caping your Up B is a nightmare, but with toon's predictable recovery, its very possible (Kirins done it to me several times before >_>)
If you Up B at a bad time and don't grab the ledge, F.L.U.D.D can be just as bad as the cape.
Don't get hit (lolIsai) unless you like being in a combo, be aware of the cape and mix up your projectile game, space your arieals, and gimp when possible.
Thats about all I got for this matchup.
P.S.
Kirin- Nair would be better for breaking out of a combo than bair, but its not very wise for toon link to attack out of a combo in the first place.