KEY INPUT FISHING MINI-GAME, PLEASE HELP POINT ME IN THE RIGHT DIRECTION.

Yeah, it's possible. What I'd recommend is setting up two events. The first one is the passcode event. It basically grabs the correct key's input using that event command (I forget the name of it in 2K3). You'd just have one of those for each key that needed to be pressed.

The other event would run in parallel and essentially kill the other event if time ran out.

Let's say the start of it all is just an ordinary event triggered by the action button.

That event would first set a random value to a variable.
Then make branch conditions for each value = each fish.
Inside each branch, show pic (fish pic, key sequence pic)
Trigger a switch
That switch will turn on another event, a parallel event.
That event should have one page for each fish.
First thing of this event is a key input process. Set the value of the key into a variable (KEY).
You need another variable to determine which part of the sequence the player is in (first key, second key, etc.). Let's call this variable ORDER.

Now use branches.
Suppose the first key is down (1) then up (4).
Cond ORDER = 1
Cond KEY = 1
ORDER + 1
else
Terminate event
Cond ORDER = 2
Cond KEY = 4
ORDER + 1
else
Terminate event

etc

When you select the key input command, you choose one single variable. Every time the player presses a key, a corresponding number will be set to that variable.

Just click "key input processing" and you'll see how it works.

Cool, I will do a fishing minigame myself. I haven't thought of the system yet, but it's interesting to see another's take on it. For which game is this? Any chance to see it in-game?

This will probably just make the game freeze, but if you don't want them to move you could try setting it to Autorun.

do you have the "wait until key input" box checked?
do you have some event further down the road that halts the repetition of the event?

and aside from that, then this would prove as a perfect example of something which could be used to practice the pointers of rm2k3.
by listing up the different keys of the sequence into a list of variables and having a variable refer to their ID's

let's say you the sequence keys span over variable 21 to 28, then you'd have the sequence order variable start at value 21, you have a key comparison variable which takes the value of the index of the sequence order variable (right below the option which let's you use the value of a variable) .
you check if the input key equals the key comparison variable and increase the sequence order by 1 as you already do.

the advantage of doing this now won't be much except from reducing the amount of code considerably, but the practice using pointers and knowing how to using them can come very handy to future mini games you might wanna make.