Muniz also admitted that he's never gotten a professional opinion on his memory struggles. "I've never been to the doctor and been like, you know, 'Why don't I have a memory?'" he said. "To be honest, I've never really talked about it."
To help him remember, the actor-turned-race car driver said that his girlfriend, Paige, writes down everything they do each day together in a journal.
"I love to be able to look back," he said of the journal. "It makes make a little sad that it doesn't just pop back into my mind. Like, I should have remembered going to Australia. That's something that people remember."
"I told him not to worry about what you remember and what you don't remember. They're still your experiences," Cranston said. "That will be my job. I will tell him, 'Remember this? Remember that from Malcolm? What a life for you!'"
"My most memorable year is 2017, because I learned to live in the present," Muniz explained. "I'm happy with my acting career, I'm happy the decision I made to drive race cars and to focus on music. Even if I don't remember it all, I'm happy."
Taking to the DWTS stage, Muniz and Carson performed a fun, energetic quickstep set to Coldplay's "Adventure of a Lifetime" and the sweet dance won over the judges, who praised the star for his spirit and determination.
For their efforts, the pair earned a score of 24 out of 30, which is an improvement over their marks last week.
After getting some feedback from the judges, host Tom Bergeron asked Muniz about his health issues and memory battle. "You seem to be almost at peace with the fact that you're having memory issues," Bergeron said. "Is that accurate or is that just acting?"
"No, 100 percent. I mean, it's not something that I necessarily think of. I'm just me, so I only know my brain and my life. But it's weird when I talk to family or friends or people who I've worked with and they bring up things that I don't quite grasp unless I see pictures and videos and stuff."
ET's Cameron Mathison caught up with Muniz after the show, and he opened up about what it meant for him to see his TV dad appear in the DWTS package to show his support.
"It was awesome!" Muniz marveled. "He's in London for the next month but the fact that he even did the interview, I was so grateful, because he's such a great guy and so supportive of everything I do. He's awesome."
Earlier this season, Muniz opened up to ET about his health struggles, including his physical therapy to help ease pain stemming from a car crash that broke his back several years ago.
"I want to make sure we are ready, so there is a fine line of, how hard do you work to how hard do you take care of your back," he explained. "We rehearse five hours, but then I spend about seven hours literally trying to heal, doing whatever I can."