The veteran TV presenter appeared on the hugely popular Channel 4 show alongside his famous daughter BBC Radio 2 DJ Zoe Ball and grandson Woody Cook, but viewers had no idea he was part of the star-studded line-up and took to Twitter to share their shock and delight after tuning in.
WATCH: Johnny Ball leaves daughter Zoe in stitches after comment on Love Island
"Love @C4Gogglebox and #CelebrityGogglebox. Was happy to see Jonny Ball on there tonight. Great man still funny," one thrilled fan wrote as another said: "@C4Gogglebox JOHNNY BALL!!! You've made my night."
"Johnny Ball making Woody and Zoe cringe is hilarious. Highlight of tonight's #CelebrityGogglebox," another commented, and a fourth added: "More Johnny Ball please!"
Many more viewers were left gobsmacked after the TV legend and mathematics maestro made a comment about how old he is. After Johnny, along with his daughter and grandson, watched an episode of Love Island, he was asked whether he would ever appear on the reality show.
Johnny Ball appeared alongside daughter Zoe Ball and grandson Woody Cook
No stranger to reality television, the former Strictly Come Dancing contestant responded: "Erm, I might find it exhausting at my age, to be honest." After puzzled looks, he added: "Because I wouldn't like to leave anybody out," which prompted Zoe and Woody to burst into laughter.
Fans also found the moment hilarious - but more than that, they were left amazed after looking up Johnny's real age. "Johnny Ball … 84, unbelievable," someone remarked, while another wrote: "Johnny Ball doesn't look a bit different than he did on Think Of A Number!! #Gogglebox."
While Zoe and Woody have appeared on Celebrity Gogglebox before, it was Johnny's debut appearance on the reality show.
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