My grandson forgot his password and weight he entered in Wii Fit. Is there any way to reset password or do we have to delete his character?
Try clicking on the Mii and after it asks for a password, just guess and type in something a few times and you should get a message asking if you "Are you really [insert name here]?":)
If you say "Yes" and it will ask you for height as a confirmation, so since your grandson can not remember, you'll have to systematically guess (4 foot one...4 foot two...etc...) and hopefully you will be lucky and hit the right height sooner then later and should be able to then enter the profile and delete it.:)
However if that takes too long and doesn't seem to work, then you could delete all the profiles and restart Wii Fit right from the beginning again, by erasing the Wii Fit memory save on your console.
If that is what you decide to do, then click on the "Wii" icon on the lower left-hand of the menu screen.
Then "Data Management", under "Save Data" you will find the "Wii" memory saves and Wii Fit.