Does anyone from seasaon 1 and 2 of digimon ever show up in the other seasons?

Yes, there are a few characters from Digimon Adventure (season 1) and Digimon Adventure 02 (season 2) who appear in other seasons. Here are some notable examples:

* Tai Kamiya: Tai appears in Digimon Adventure tri. (season 6), Digimon Adventure: Last Evolution Kizuna (season 7), and Digimon Adventure: (reboot).

* Matt Ishida: Matt appears in Digimon Adventure tri., Digimon Adventure: Last Evolution Kizuna, and Digimon Adventure: (reboot).

* Sora Takenouchi: Sora appears in Digimon Adventure tri., Digimon Adventure: Last Evolution Kizuna, and Digimon Adventure: (reboot).

* Izzy Izumi: Izzy appears in Digimon Adventure tri., Digimon Adventure: Last Evolution Kizuna, and Digimon Adventure: (reboot).

* Mimi Tachikawa: Mimi appears in Digimon Adventure tri., Digimon Adventure: Last Evolution Kizuna, and Digimon Adventure: (reboot).

* Joe Kido: Joe appears in Digimon Adventure tri., Digimon Adventure: Last Evolution Kizuna, and Digimon Adventure: (reboot).

* T.K. Takaishi: T.K. appears in Digimon Adventure tri., Digimon Adventure: Last Evolution Kizuna, and Digimon Adventure: (reboot).

* Kari Kamiya: Kari appears in Digimon Adventure tri., Digimon Adventure: Last Evolution Kizuna, and Digimon Adventure: (reboot).

* Davis Motomiya: Davis appears in Digimon Adventure tri. and Digimon Adventure: Last Evolution Kizuna.

* Yolei Inoue: Yolei appears in Digimon Adventure tri. and Digimon Adventure: Last Evolution Kizuna.

* Cody Hida: Cody appears in Digimon Adventure tri. and Digimon Adventure: Last Evolution Kizuna.

* Ken Ichijouji: Ken appears in Digimon Adventure tri. and Digimon Adventure: Last Evolution Kizuna.

These are just a few examples. There are also some other characters from Digimon Adventure and Digimon Adventure 02 who make small appearances in other seasons or movies. However, the characters listed above are the most prominent ones who reappear throughout the Digimon franchise.

It's worth noting that the later seasons (particularly Digimon Adventure tri. and Digimon Adventure: Last Evolution Kizuna) often reference events and characters from the earlier seasons. So, even if certain characters don't physically appear, their influence and impact are still felt in the later stories.