Keys' outburst came during Tuesday night's Champions' League quart-final against Barcelona.
To his relief, only fans listening to Sky Sports online streaming of the 4-1 defeat heard the gaffes.
Oops: Keys could be heard on Sky's live online internet streaming criticising the Arsenal winger
At one point when Walcott went down under a challenge, Keys was heard saying: 'Get up, you stupid little boy'.
As commentators Martin Tyler and Andy Gray described the game, Keys could be heard saying: 'You've been s***e, son, in your daft pink boots - absolute rubbish.'
To make matters worse, he was first be heard asking his studio guests who was responsible for breaking wind.
Sitting alongside twice European Cup winner Ruud Gullit, and Graeme Souness, Keys said: 'Who's farted? It's not me.'
Keys has previous, too. In 2007 during a Scotland match in the Faroe Islands, the commentator was heard on air to say: 'Silly ground, stupid game, f*** off.'
Critique: Eric Abidal of Barcelona is challenged by Theo Walcott of Arsenal during the UEFA Champions League quarter final
On Wednesday a Sky spokesman said: 'There were no technical issues with the audio on the night.'
The gaffe comes just days after pundit Chris Kamara was hilariously caught missing a red card at the Portsmouth vs Blackburn Premiership match.
During Sky's live results programme Sports Saturday, presenter Geoff Stelling cuts to Kamara live at Fratton Park for news of a sending off.
But a bemused Kamara is forced to admit he was aware of anyone getting a red card.
As studio pundits Matt Le Tissier, Phil Thompson and Charlie Nicholas howl with laughter, he adds that he though Anthony Vanden Borre had been substituted.
A clip of the incident has become a massive internet hit, gaining more than 100,000 hits on YouTube.