Mario Kart: Double Dash Cheats

First get a mushroom and save it then when you come across a tunnel after the long yellow bridge go right you see a gap. Use a mushroom to get across the gap.

Ok to get to the shortcut you have to go where you can go either right or forward. Go forward then turn left quickly and you will see a narrow path. That's the shortcut!

These are all the characters you can unlock.

(You will need a mushroom for this shortcut.)
Choose Yoshi's Circuit as your track. To cut across Yoshi's spine, when you come out of the second tunnel, a little bit out you will see a space in between the rail and the rest of the track. Now use your mushroom, and speed yourself off the ledge. If your timing was right, you should get ahead by alot!
(P.S If you miss, say hello to a watery grave!)

Beat these record times to unlock a staff ghost racer for each track.
Baby Park: 1:14.000
Bowser's Castle: 2:47.000
Daisy Cruiser: 1:55.000
Dino Dino Jungle: 2:03.000
DK Mountain: 2:15.000
Dry Dry Desert: 1:53.000
Luigi Circuit: 1:29.000
Mario Circuit: 1:44.000
Mushroom Bridge: 1:34.000
Mushroom City: 1:53.000
Peach Beach: 1:15.000
Rainbow Road: 3:19.000
Sherbet Land: 1:28.000
Waluigi Stadium: 2:02.000
Wario Colloseum: 2:24.000
Yoshi's Circuit: 2:02.000

Once you have received the gold trophy on Mushroom, Flower, Star, Special Cups, and The All Cup Tour on 50CC, 100CC, 150CC, and Mirror mode, you will be rewarded with a new title screen featuring all of the racers. Now you get to see all of the characters and the new cars on your title screen!

Well I have a few unlockables here. These are some of the basic unlockables. I hope you like them!

Before the race starts, wait until the light turns green, and just
before the words "Go" appear on the screen, hit A and you'll start the
race much faster and get a big boost, and a big starting lead on all
other opponents.

The Speed rating is, of course, the top speed of each vehicle. Note that the top speed averages only vary 1 to 2 mph per star, but over 3 laps, it all adds up. The Kart's weight factor will not only determine how much you slow down if you go off course, but also how much speed you will lose by making a turn without power sliding. For example, Bowser's Kart may have a ***** rating on speed, but the ***** rating on weight tends to make him lose more speed unless you power slide into your turns. The rule is, the heavier you are, the more power sliding will be necessary to keep that nice top speed bonus. Remember, the difference is fractional, but after three laps it all adds up. Other factors in-race that will alter your top speed is turning without power sliding (it will knock you down 1-2 mph), incline of the road (down-slope faster, up-slope slower), and turning while power sliding (which will actually raise your top speed 1 mph if you sustain it) will not lower your speed at all. The class speed breakdown is as follows. Note: This is an average. One star of weight more or less will alter the speed 1 mph or so respectively:
 
50cc 100cc 150cc/mirror
* 42 mph 47 mph 54 mph
** 43 mph 48 mph 55 mph
*** 44 mph 49 mph 56 mph
**** 45 mph 50 mph 57 mph
***** 46 mph 51 mph 58 mph
Note: It does not matter who you have driving; speeds remain the same no matter what character you choose to drive.

When you fall off the track, when the little cloud man bring you back to the track, if you press the gas button right when the wheels touch the ground, you'll also get a little boost. Courtesy of fUble_baSs.

You get a boost at the start if you press A right after the lights turn green. You can also get a much larger boost though in co-op when both players press A at the same time. Courtesy of Duncan.

To receive a boost at the beginning of a race, hit A at the same time the announcer says go. If timed correctly, you will jump to the head of the pack.