Once they mentioned time travel I immediately knew this was going to be a fanservice movie with throwbacks designed to elicit nostalgia.

Anyway one huge plot hole. I thought they said each avenger only had enough Pym particles for one return trip each. So how did nebula's Pym particle become enough to transport thanos entire freaking army over?

Russo edy addressed this question. Ebony Maw was able to replicate the formula.
Turns out you only need grape juice, jello and sugar.