"Of course on a Friday night," the actress joked, adding that she blames “pizza” and herself "for not planning ahead"
On Friday night, the 6-year-old lost one of his front teeth, and Spelling, 50, documented the entire saga on her Instagram Story.
Alongside a photo of Beau holding his mouth open to showcase his toothless grin, the Beverly Hills, 90210 alum wrote, “Lost his front tooth tonight. I think his wish might come true.”
“Of course on a Friday night,” she continued in the next slide, a picture of Beau holding the tooth in his palm, sharing that she blames “pizza” and herself "for not planning ahead.” Spelling seemed to imply she didn't have any money on hand to leave for Beau from the Tooth Fairy.
“#MOMFML,” she added.
With a final, smiling shot of Beau, Spelling shared a funny interaction that the mother-son duo had after he lost the tooth.
According to the actress, she told Beau that the Tooth Fairy may not be able to travel in the “pouring rain,” to which he replied, “Mom. She’s magic and she can just put on her raincoat.”
“Oh, right,” she responded. “Does a hoodie work? Asking for a friend.”
When Beau celebrated his birthday in March, the star shared a sweet tribute dedicated to him on Instagram.
Alongside a video highlighting moments in her pregnancy with Beau and some early moments in his life, she wrote, "Can't believe my baby is 6 today."
"Beau is the light and soul of our entire family," she continued. “He brings such joy and laughs into my life, his dad's life, and all of his siblings. Finality is a hard thing for me. Knowing Beau was the last was tough because I love the journey of pregnancy so much. And, every second of motherhood.
“But knowing Beau in the physical sense for 6 years now it all makes perfect sense. He completes all of us. He is so special. So kind. So smart. And, so darn funny! We celebrate you everyday Beau Beau Bear! I love you with all my heart.
“I always thank all of my babies for choosing me to guide and love them thru this lifetime. I thank you Beau for this final gift of motherhood. We are a good pair. My cuddler. My love!” she finished. “I love you forever, Beau Dean.”
In addition to Beau, Spelling also shares Liam, 16, Stella, 15, Hattie, 12, and Finn, 11, with ex Dean McDermott.
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Last September, the actress opened up to PEOPLE about how raising kids who are different ages — and thus at different life stages — comes with unique challenges.
Spelling told PEOPLE that all five of her kids are "evolving every day."
"They're constantly changing, they're learning,” she said at the time. “They're not stagnant and I feel like as adults sometimes we get to that place. "We get boxed in by other people, and the boxes we put ourselves in.
She continued, “Kids don't do that. They'll be like, ‘Hey, today I love this,' and next week, they'll say, 'I'm into something else.’ They try new things and explore, so I try to look at things through their eyes.”
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