The Gabon worldwide was cup-tied for the Europa League victory over AC Milan on Thursday, but returns to the fold against the Hornets, with the Gunners aiming to halt a run of three straight Premier League defeats.
The 22-year-old Bellerin, who sports a ponytail, obviously hadn't forgotten Deeney's dig and when Petr Cech saved the Watford skipper's spot-kick on Sunday, he got one over the English striker with his sly tweet.
The Gunners may finish the campaign without a player in double figures for league goals for the first time since Harry Woods top-scored with nine in 1923-24: Alexandre Lacazette has nine but is injured while Alexis Sánchez, next on seven, has left.
Gunners fans has never forgotten Deeney (rightly) saying that Arsenal were lacking "cojones" when his side beat them 2-1 at Vicarage Road in October.
Cech's penalty save was his first since joining Arsenal in 2015 and it helped him secure a landmark 200th Premier League clean sheet.
Wenger's men welcome AC Milan to the Emirates on Thursday, with a 2-0 lead to protect.
However, Arsene Wenger's men didn't have to wait long as German World Cup victor Shkodran Mustafi was able to find the back of the net after eight minutes.
The victory over Watford does however mean the Gunners have won two on the bounce, having ended a four-game losing run with the 2-0 win over Milan at the San Siro on Thursday.
'In the end it was a convincing win, ' he said. They attacked well in the first half, and an eager Ozil looked frustrated at times as he failed to make anything of a couple of decent chances, at times hindered by the quality of passing from his team-mates. "But overall the spirit and desire was good". It also shows remarkable intelligence because without remarkable intelligence you don't last in the game, because you have to deal with so many different problems.
Petr Cech (Arsenal): It's been a tough time for the keeper, who was forced to accept some responsibility after a awful result last weekend against Brighton.