The Good Morning Britain star revealed she had a "calamitous few days" in the lead-up to the festive season.
A chart-topping pop star, Loose Women duo and award-winning rapper are also taking part.
Giovanna's close pal Emma Willis came up with the suggestion.
Brian accused Big Brother: Best Shows Ever of "trying to rewrite history" earlier this week.
Fans rewatched the episode that saw Craig Phillips confronting Nasty Nick during the first series.
Emma Willis and Dermot O'Leary will also be joining in the fun on Big Brother: Best Shows Ever.
Gary Lineker opened the show revealing a chunk of money would be donated to those affected by the coronavirus outbreak.
The grand finale saw Emma slipping back into old habits.
The former Big Brother host is taking over from Maya Jama and Alice Levine.
She is best known as the host of Channel 5's incarnation of Big Brother.