Nostalgia often brings up happy memories... except when it's trying to steal your husband!

American Housewife will welcome guest star Tiffani Thiessen to Westport in Tuesday night's episode, but the Saved By the Bell and Beverly Hills 90210 vet may be up to no good.

Thiessen will play Celeste, the ex-wife of Angela (Carly Hughes), who uses her position as a publishing editor to help Greg (Diedrich Bader) sell a book. But problems arise after Angela asks Katie (Katy Mixon) to not socialize with Celeste, and accuses Katie of being a bad friend when she does.

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But that might be the least of the problems. In this exclusive clip of Thiessen's guest appearance, we see that someone even closer to Katie may be socializing a little too much with Celeste. Girl, you already had Zack Morris, do you really need to take Greg, too?

American Housewife airs Tuesday nights at 8:30/7:30c on ABC.