Cape (スーパーマント Sūpā Manto Super Mantle) is Mario's side special move. Dr. Mario's version is the Super Sheet. Either has the ability to reflect projectiles and spin characters in the opposite direction. In Melee, the cape can flip shielding opponents, but only if they've power-shielded the attack. In Brawl, Pit's move Mirror Shield causes a similar redirection of characters, but only if an attack connects (at close range) with the shield.
The Cape deals up to 10% damage (12% for the Super Sheet), has no knockback and doesn't make the opponents flinch unless the cape is used on an opponent attempting a grab (then, knockback increases only slightly, while not enough to KO. Characters hit with the cape while attempting a grab will be sent spiraling a short height into the air). This means that it will not interrupt attacks; rather, it only turns the enemy character around. This can leave recovering characters unable to grab the ledge. This has less use in Brawl thanks to the "Auto-Snap" feature that means characters will grab a ledge regardless of which direction they are facing. However, the cape can be broken in the same manner as a reflecting attack can. That is to say, if the damage that the oncoming attack would do would break a shield in one hit, the cape will not work and Mario or Dr. Mario will enter broken shield animation.
If used on someone in Brawl while flying because of an attack, it multiplies the distance by about 1.6. Using the Cape also causes Mario to float slightly, meaning it has uses in recovery and in helping him avoid edgeguarders.
 Super Sheet
Super Sheet is the side special move Dr. Mario uses in Super Smash Bros. Melee. This attack is almost the same as Mario's Cape attack - the differences are that Super Sheet is longer and does slightly more damage than the Cape (up to 12% rather than 10%) and has less lag, but moves Dr. Mario up only once, making it less useful for recoveries. The attack can also be used to shift the direction of a player who is trying to get back on the field. In this case, they will be turned around, and will instead jump back on air, rather than jump on the field.
 Cape jump glitch
The Cape jump glitch is a glitch that only Mario can perform in Melee and Brawl. This glitch occurs when Mario uses his Cape on an enemy that is increasing their height (jumping, mid-air jump, recoveries, footstool jump etc). The enemy will increase their height much higher than normal.
Originating from Super Mario World, the Cape was a power-up obtained from the Cape Feather, which enabled Mario (and Luigi) to spin and attack with it (although Mario did not hold the cape in his hand during the spin attack, as he does in the Smash games), as well as flying great distances after a running start and floating softly back to earth when falling. Mario did not "fly", rather, but "glide", but could do so more or less infinitely by diving and pulling up in a certain rhythm, and while gliding he could slam into the ground to create an earthquake capable of damaging all enemies on the screen. This is, of course, not present in the Smash games.