Why weren't some of the original Digimon able to evolve into their Ultimate/Mega forms in season 1?


Up until Digimon Tri, only two people from the original Digi-destined were
able to evolve their Digimon to their Ultimate/Mega form (and even go beyond
that, see [Omegamon](http://digimon.wikia.com/wiki/Omnimon)). All the other
characters were stuck with Digimon that could only go up to Perfect/Ultimate
form. I get why, it's explained in episode 38 of season 1.

But why has that changed in Digimon Tri? How can Joe and Mimi evolve their
Digimon into Ultimate/Mega forms so easily? What made it possible for them in
Tri that wasn't possible for them in the original season?




Based on the [Digivolution](http://digimon.wikia.com/wiki/Digivolution) wiki,
Agumon and Gabumon didn't quite perform a Mega Digivolution - they performed a
_Warp_ Digivolution.

> Warp Digivolution is a digivolution process where a Digimon can reach a
> higher level directly bypassing any intermediate phases

When Tai and Matt were shot with the Angelic Arrows, Agumon and Gabumon wrap
digivolved to their Mega forms. During the digivolvution scene, they say

> Agumon/Gabumon **warp** digivolve to WarGreymon/MetalGarurumon

Furthermore, Warp Digivolution and Mega Digivolution are not the same thing.
While see Mega forms in season 1, regular Mega Digivolution is actually not
seen in Season 2

> Mega Digivolution is a Digivolution method that allows an Ultimate Digimon
> to digivolve to Mega. **It is initially used by Paildramon to digivolve to
> Imperialdramon in Digimon Adventure 02.**

In the episode [Determination](http://digimon.wikia.com/wiki/Determination),
the digidestined were also shocked to see the fact that Gomamon was able to
achieve his Mega Digivolve of Vikemon.

> Joe realizes that his relationship with Gomamon is the more important thing,
> and so he charges back to the battle. This rebirth of confidence allows
> Gomamon to achieve his Mega level, Vikemon, **much to everyone's surprise**

Explained in Season 2 a strong bond between two individuals is required to
perform DNA Digivolve, and it is possible such bond is able to achieve Mega
Digivolution.

> Seeing Joe's resolve, Mimi regains faith in herself as well and helps
> Togemon her own Mega level in Rosemon.

As we see in the following episodes, there is a continuation of strong,
emotional connections between the digimon and digidestined.

[Confession](http://digimon.wikia.com/wiki/Confession)

> Izzy pleads with Tentomon to enter the shield, but Tentomon refuses to do so
> while his friends are suffering. He digivolves to his Mega form,
> HerculesKabuterimon

[Loss](http://digimon.wikia.com/wiki/Loss)

> Sora risks her life to protect Biyomon from Machinedramon, digivolving her
> into her Mega form, Phoenixmon

