Yes because big bird has a secret personality that turns him into lucifer. It can be accesed by prompting him with cookies. This is the reason that big bird and cookie monster never appear at the same time. During Sesame Street and the abc's the videogame there is a secret number counting level where you can prompt big bird to perpanatly become lucifer/big bird.
Because first of all, his NAME is COOKIE monster and he likes his cookies.
Cookie monster 
The cookie monster fears cookies. The cookie monster fears maddy because she is one evil cookie loving monster with 8 legs...
ANY KIND!!! COOOOOOOOKKKKIE !!! The Cookie Monster was well known for loving a diverse range of cookies.
Who doesn't love cookies? Everyone loves cookies. Except for, of course, cookie-intolerant people don't like cookies and nor do the cookieless sphingus tribe who live in the Bahamalayan mountains.
random children
Because first of all, his NAME is COOKIE monster and he likes his cookies.
Cookie monster 
The cookie monster fears cookies. The cookie monster fears maddy because she is one evil cookie loving monster with 8 legs...
It was the Hamburglar...
me want cookies!
No! He Is a COOKIE monster, vegstables aren't exactly like cookies.
ANY KIND!!! COOOOOOOOKKKKIE !!! The Cookie Monster was well known for loving a diverse range of cookies.
Cookie Monster likes cookies the most.
Cookie Monster loves all cookies but his favorite is Chocolate Chip cookies :) Hope this helps!
gemma crowson (a.k.a cookie monster)
i think they did not change cookie monster to veggie monster i think they just have him eat veggies and cookies