The designs above and below were created by Ricardo Delgado and Guy Hendrix Dyas. "The Sentinels were considered briefly for the X-Men sequel, and I drew up a version to a great collective yawn from everyone involved." said Ricardo Delgado. As you can tell, the models we could have seen in X2 vary greatly when compared to what we saw in Days of Future Past. The sentinels here are much more clunky and robotic, while the models we saw in DOFP are slick and thin. Around the time of X2's release, Bryan Singer, the director of X-Men, X2, and Days of Future Past, told TotalFilm that "We felt, for X2, the concept of giant robots is a difficult sell. But it's definitely something we may have room for in the future.". Simon Kinberg told IF Magazine "There never was a Sentinel script that veered away from the story we ended up with. I have no idea where the rumors came from, but it may have something to do with the Sentinel in the danger room. It also might have something to do with the fact that there was an earlier draft of X-MEN 2 that had Sentinels in it.". Apparently, adding sentinels to the film would have also added another $8 million to the budget of the film, which contributed to the cutting of their appearance.