The former Nickelodeon star stirred controversy on Monday (01Jun15), after Jenner revealed her new persona on the cover of Vanity Fair magazine, by sharing his thoughts on Kim Kardashian's stepdad's news.

Bell wrote, "Sorry....still calling you Bruce."

After a backlash from some of his followers, Bell deleted the tweet, and wrote, "That's bravery!"

He continued to explain himself by writing, "Good thing social media has no effect on real life... I'm not dissing (blasting) him! I just don't want to forget his legacy! He is the greatest athlete of all time! Chill out!"

However, Bell went one step further on Thursday (04Jun15) by posting a formal apology on the microblogging site.

He wrote, "I sincerely apologize for my thoughtless insensitive remarks. I in no way meant to hurt or demean those going through a similar journey.

"Although my comments were made in innocence, I deeply regret the negative effect they've had on so many."

When one follower noted he should change his statement to "ignorance" from "innocence", Bell agreed and replied, "yes. Very ignorant."