All bets are off - did one wear a bookie hat?

Most people are familiar with the famous 'Dogs playing poker' painting. There are actually a few in the set, and they were really popular in the 1990's in many US homes, and quite a few bars worldwide too.

People remember the realistic looking dogs sat round a table in a smoky room, intently focusing on their poker game. Do you remember any of the dogs wearing a transparent green dealer's hat? Many do, but can't find it anywhere now, and so it's being classed as a Mandela effect.

There were spin off paintings where they were involved in other sports, like billiards, but it's the poker one which is the best known. People are describing every detail of the hat, right down to it's transparent green-tinted visor and wide band. Yet there's no trace of that today...

Present in later work

Like any well-liked original work, there are paintings which followed from other artists which continued the theme, and actually did show a dog wearing the green visor in question. These do not detract from them not being present in the original, although they would likely add to the confusion. Here's an example:

Cassius Marcellus Coolidge

The set of paintings were created by Cassius Marcellus Coolidge between 1894 and 1910. The later ones were used to advertise cigars, and were commissioned after the popularity of the earlier ones gained wider recognition. There were 18 in total, 11 of which show dogs round a table. The original one, title "Poker Game", sold for $658k in 2015.

They have appeared in numerous guises, such as prominent background decorations and parodies, in countless popular movie & TV shows, which is fitting considering their age. 

The reason for this Mandela Effect is probably one of an assumption. The dogs are playing poker, they are sitting round a table, wearing human clothes. The whole point is that they are behaving exactly like humans would. Those who remember the painting but not the details would remember that much at least, so when retrieving the mental image, the act of putting a dealers hat on one of them seems natural. It's only when a group of people are insisting they did not "fill in the blank", and one really did wear the hat, that the trouble begins...