Tarek El Moussa Was in Shock When Christina Haack's Second Husband Ant Anstead Showed Up on Flip Off (Exclusive)

• Christina Haack chose her second husband Ant Anstead as a surprise guest star on her new HGTV show The Flip Off
• The pair went through a bitter divorce in 2020 that involved a custody battle over their son Hudson, but have since made amends
• Christina's first husband and Flip Off co-star, Tarek El Moussa, tells PEOPLE exclusively that he was shocked his ex-wife was suddenly on good terms with Anstead

Tarek El Moussa was in for a big surprise when he found out who his ex-wife, Christina Haack, asked to join their new series. 

The HGTV star, 43, tells PEOPLE in an exclusive interview alongside Christina and his wife Heather that he was in complete shock when his ex-wife chose her second husband, Ant Anstead, to be a guest judge for their competition show The Flip Off. 

Tarek emphasizes that it especially caught him and Heather (who also stars on the series) off guard because they had no clue Christina and Anstead were even on speaking terms following their bitter divorce in 2020.

“All of a sudden they're besties,” Tarek recalls of his reaction to seeing Anstead, 45, and Christina, 41, interact on set. 

Heather adds that it “really threw us off” because they were under the impression that Christina and Ant “weren’t talking.” 

The Selling Sunset alum, 37, says watching Christina and Anstead’s reconciliation “unfold in front of our eyes” was a whirlwind experience. 

“[Christina] started following [Ant] on Instagram and we were like, ‘What? What's going on?’ It really was like that for us,” she says. “You see it transpire on TV and we're so thrown off by the situation. I think we texted her, ‘Why are you following Ant? What's going on?’”

Knowing that she would catch her rival team on the show by surprise, Christina admits to PEOPLE that a big reason why she asked Anstead to join the show was to “mess with” Tarek and Heather.

“I feel like some of [the judges] that I picked were just to mess with him,” Christina says. “It worked.” 

Fans first learned that the British automotive expert and TV host would likely be appearing on The Flip Off when he and Christina were spotted filming together in November 2024. A source told PEOPLE at the time "Ant is going to appear on the show, but he won't be Christina's partner.”

However, the sighting shouldn't have come as a shock to fans paying close attention.

A few months earlier, the Christina on the Coast star joked about Anstead replacing her estranged third husband Josh Hall on the series after his abrupt exit. Josh was initially set to be Christina’s teammate on the house flipping showdown before he filed for divorce in July 2024.

Christina and Anstead’s recently-mended relationship comes after years of tension.

The pair, who wed in December 2018, announced they were separating in September 2020 and finalized their divorce in June 2021.

After their split, they were involved in a heated custody battle over their 5-year-old son Hudson that often played out in the public eye and was finally settled in December 2022. 

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It wasn't until after Christina’s third husband Josh filed for divorce that she and Anstead started to become friendly again.

The first step was Christina re-following him on Instagram, followed by Anstead reciprocating the gesture. In recent months, they've been tagging one another in Stories about Hudson and exchanging kind words in their Instagram comments.

The HGTV star did offer some insight as to why she wanted to be on better terms with her ex. One month after her split from Josh, she explained to Backgrid that it was a conscious choice made for Hudson's benefit, as he "deserves to have us get along.”

While Christina has made amends with Anstead, her relationship with Josh remains tense.

The pair have been publicly speaking on the drama between them in various social media posts since their breakup. Amid their ongoing divorce, both have also entered new relationships: Christina with businessman Christopher Larocca and Josh with model Stephanie Gabrys.

The Flip Off airs Wednesdays at 8 p.m. ET/PT on HGTV.