The tribute by the royal couple didn't go unnoticed by royal fans, who according to the Daily Mail, said it brought back "great memories" of Prince Harry as a child.
The publication reported that one observer wrote, "'Love when they channel past looks!" while others noted the striking resemblance the father and son shared.
"So alike in these pics!" said one fan, followed by another who wrote, "Archie is 100% his father."
WATCH: Baby Archie seen wearing knitted bobble hat as Duke and Duchess land in Cape Town
Observers of the royal family also believe Prince William and Kate Middleton are expecting their fourth child after she dropped a clue as well.
The 37-year-old was pictured with a new hairstyle while taking Princess Charlotte to her first day at school two weeks ago, sparking pregnancy rumours online.
In the past, the Duchess of Cambridge has been known to do this before announcing a pregnancy (she made changes to her hair prior to breaking the news of her pregnancies with Prince George and Princess Charlotte).
"Like a lot of women Kate does tend to change her hair when she is pregnant, although not dramatically," Body language expert Judi James told Daily Star Online.
"The new style and colour she emerged with when she took George and Charlotte to school did look like one of her glossiest and most fashionable looks to date.
"But then she did say she’d had it done for the school run, and it could have been aimed at giving her an emotional lift as Charlotte left home for school for the first time."