the campfire scene.

[Mirenately]

Hm...And don't they need a gate key just to activate the portal? Is it necessary to have it to travel through the gate? If the answer is "no" then only one person, who holds the gate key, can send others through the gate and, after that, travel through time by him-/herself.
All we know about the max number of people who can go through at once. But the game itself shows (when Lucca arrives in 600 A.D. on her own) that individual time traveling is quite possible.
So the question is: for what exact purpose do they need a gate key?

[maggiekarp]

...How come none of us remembered that Robo and three other party members were already in Fiona's Forest at the time?

[Acacia Sgt]

So the question is: for what exact purpose do they need a gate key?

The Gate Key is what opens the gates. Name explains use.

...How come none of us remembered that Robo and three other party members were already in Fiona's Forest at the time?

That's a good point, I guess they went with other variables of the situation. Then just have the other three use a gate.

[Chrono'99]

Hm...And don't they need a gate key just to activate the portal? Is it necessary to have it to travel through the gate?

It's not necessary, as shown by the main ending when each character goes in the Telepod Gate while Crono, Marle and Lucca stay and presumably hold the Gate Key.

[mav]

Anyhow, who is to say that they all used the same gate to get to the campfire anyway? I don't really see an issue here...

The Gate Key, they only have one, so they also have to use the Epoch. That leaves one party member still in the EoT though, which is why one of either group has to go back for him/her.

Of course, I kinda forgot about that Gate Key...

And it looks like MaggieKarp solved this conundrum anyway.

[radicalblues]

Imagine you have Crono, Lucca, Marle and Robo in a group. You are in the end of time. Now imagine you push all 4 through any gate at the end of time... they would travel through time in the gate, but due to principles, the gate would send them back to the end of time... and they'd land in the same portal!

Infinte loop!

[Mr Bekkler]

Imagine you have Crono, Lucca, Marle and Robo in a group. You are in the end of time. Now imagine you push all 4 through any gate at the end of time... they would travel through time in the gate, but due to principles, the gate would send them back to the end of time... and they'd land in the same portal!

Infinte loop!

Hence the thread.

[Acacia Sgt]

Indeed, that would cause a serious trouble if done that way. However, since it's the EoT itself the starting point, who says the voyage can't be done if it's tried from the very place it should bring you to?

Not sure if it makes an exception or it does keeps the rule.