Friends and family gathered around as Will, dressed in safari gear, and his pals got up close with a baby alligator and an armadillo brought in by zoo staff.
Will squeals when asked if he wants to pet the alligator, featured in this sneak peek of Tuesday’s episode, airing at 10 p.m. on TLC.
“Thankfully, the alligator was a baby and no one lost a finger,” Arnold jokes.
This year has been one of many milestones for the couple as viewers watched Arnold, a neonatologist at Texas Children’s Hospital, go through her diagnosis of a rare cancer, intensive chemotherapy treatment and remission.
As the family dealt with Arnold’s health scare, they also welcomed daughter Zoey, 2, adopting her from India. Zoey, who has acclimated well to her new family after an initial bumpy transition, took a nap at her big brother’s birthday party.
“Jennifer grabbed her and she took a nap,” says Klein in the episode. “That’s okay, she’s 2.”
Arnold and Klein say they will celebrate both children’s birthdays and adoption dates – Will has been home for a year now, since March 5, 2013 and his birthday is in February.
“No matter what comes up, we are a family,” Klein told PEOPLE after Will’s adoption. “I felt that way months before Will came home. We are in it for the long haul. Every day is a new adventure. It’s exciting.”