'Bubble Boy' Seth Lane Undergoes Gall Bladder Surgery

— -- March 27 was a big day for 'Bubble Boy' Seth Lane, the 5-year-old who was born without an immune system.

Trending worldwide, the social media campaign #WearYellowForSeth grabbed the attention of Seth fans from all over the globe.

Today, Seth embarks on the first step towards having the bone marrow transplant that could potentially save his life.

"He's doing generally okay," mom Leanne Lane told ABC News. "He’s having an operation today to have his gallbladder out so so he can have his chemotherapy. He's in there right now.

"This is new for us. He's never had any operations on his organs before. He gets upset. He just says 'mummy and daddy' over and over again, but we’ll be outside waiting until hes awake."

Despite her little boy having to go through surgery today, Lane says that Seth was overjoyed about the amount of people who wore yellow for him on Friday.

"Friday was amazing," she says. "The hospital did a lot there, even the local firemen came to see him and put a ladder up to his window. He [Seth] was shell-shocked.

"It was so busy, we couldn’t even keep up. Obviously there was Ashton Kutcher and 'Paw Patrol.' They did all pups in yellow and sent him a voice message. Seth thought it was brilliant.

"On Saturday morning he said 'is everyone going to wear yellow again today?'"

Celebrities like Joe Jonas and Fifth Harmony's AllyBrooke joined Kutcher in wearing yellow. Television crews, retail stores, and even the cast of "Sesame Street," tweeted in support of Seth.

"There was a time difference between the UK and America and once America woke up, it went crazy again," Lane says. "It's really hard to put that in words. We just want to say thank you.

"He's one little boy in England who's five years old and it makes us feel amazing that people care so much. On Friday and Saturday Seth spent the whole day out of his bed and it really picked him up.

"People have been messaging me saying it's inspired them to register to give bone marrow. If they can help one person that’s amazing."

Seth's gall bladder surgery was slightly delayed because of a chest infection.

Lane told ABC News that Seth has come out of surgery and he is on the road to recovery.

If all goes well, Seth's doctors will perform the bone marrow transplant in three to four weeks.