Jeff the Land Shark, a cute land-dwelling shark, first became associated with Deadpool through the comics. Jeff was introduced in the 2018 comic series West Coast Avengers. Created by Kelly Thompson and artist Daniele Di Nicuolo, Jeff was initially part of the West Coast Avengers team. Jeff's association with Deadpool began when Thompson, who later wrote for Deadpool, brought Jeff along into the Deadpool storyline when she took over as the series writer with Deadpool (2019) #1.

In Deadpool (Vol. 7), Jeff accompanies Deadpool on his adventures, becoming a fan-favorite character due to his adorable appearance and playful nature. The addition of Jeff provided some cute and humorous aspects to Deadpool's typically violent and chaotic escapades.

If you would like more details about Jeff's appearances, you might want to check out the West Coast Avengers series or the Deadpool run starting from 2019 where he frequently appears.