Taking control of creatures with Fast

[rigid prairie]

If a player takes control of a creature with Fast (such as using Brain Fly or Mother Harpy), can they instantaneously attack or use that creature's action? I would guess no cause the Fast description says "this creature may attack [...] the turn it comes into play." and controling a creature doesn't count as "come into play". At least, when you control a creature, the Play effects doesn't trigger, so this might be similar. What do you think?

I want to clarify that I use the card game, not the computer game so I have no idea how the pc solves this interaction when playing there

[marble cypress]

"the turn it comes into play" means the turn the card is played

so if someone mindbugs it, he is considered as playing it, so he may attack with it

[rigid prairie]

The rules specifically name about Mindbug, but what about Brain Fly or Mother Harpy?
The rules mention on those cards that the Play effect don't "reactive" so I assume the same for the Fast effect

[marble cypress]

if you simply "take control" of the card using a "take control" effect, then the card is not considered as being played, so it cannot activate its FAST ability

[rigid prairie]

Thanks, that is what I wanted to confirm

[tacit kraken]

If I steal a creature that has FAST and also an activated ability:
Do I have (to attack) or use its ability right away when I Mindbug it, or can I do that later on in that turn (a bit like passing priority in MtG f.e.)?

[marble cypress]

Fast do not activate when you take control of a card. Only when the card is played.
In case you mindbug it, you have to do the action just after it was mindbugged. If you do not do it, that means you skip it forever.