Big-Cheep Cheeps (formerly known as Mega Cheep-Cheeps) are enemies in New Super Mario Bros. Wii who also appear in Mario Party 8. They are a larger sub-species of Cheep-Cheeps. They behave exactly like other Cheep-Cheeps which is just swimming around, however, because of their size, they increase the risk of Mario touching one and being damaged/killed. Just like how Fireballs and Starman can defeat Cheep-Cheeps and ice balls can freeze Cheep-Cheeps, this also goes for Big Cheep-Cheeps. They can be defeated with the same things that defeat regular Cheep-Cheeps and also can be frozen. Just like regular Cheep-Cheeps, any contact with them, makes the player lose a form or even be killed if at small form. One thing in New Super Mario Bros. Wii, is that Big Cheep-Cheeps appear to be just slightly bigger than Cheep-Cheeps. The same goes for Mega Deep-Cheeps who appear to be just slightly bigger than Deep-Cheeps. Also, Big Cheep-Cheeps are just as common as Cheep-Cheeps, who are all common enemies in NSMB Wii. In Mario Party 8, a Mega Cheep-Cheep and other Cheep-Cheeps chase the losers during the minigame, Rowed to Victory. There is a large Cheep-Cheep in Mario Party 9 that appears as a boss, however its name is "Cheep-Cheep" not "Mega Cheep-Cheep", even though it could be the size of a Big Cheep-Cheep.
Since it is fairly difficult to tell the difference between Cheep-Cheeps and Big Cheep-Cheeps, there is one way to tell them other than their size difference. Big Cheep-Cheeps' eyes, pupils and pink mouths can be seen much easier (they are bigger than that of Cheep-Cheeps) than that of Cheep-Cheeps.
This picture shows a close-up of two Big Cheep-Cheeps.
A Big Cheep-Cheep, as it appears in World 4-4.
All the fish here are Mega Cheep-Cheeps. In the picture, Mario has just received the second Star Coin of World 1-4. An Urchin and part of a Clam (they are known as Clampies in NSMB Wii) can also be seen.