Merry and Pippin are in a bit of a bind. In all the confusion it seems our two hobbits ran into a group of orcs, and even Merry separating a number of them from their hands wasn't enough to dissuade the orcs from their new captives.
The orcs are quite fractious. The whole taking captives thing really isn't their bag, but there's also an understanding of politics and power games as they challenge the power of Saruman vs Sauron. It's easy to forget that orcs are more than mindless marauders, rather than a dark mirror of the elves. The orcish argument comes to violence, but at the same time there is a call for resolution not simple slaughter. "Put up your weapons!" shouted Ugluk. "And let's have no more nonsense!"
Pippin demonstrates incredible presence of mind. In the midst of a full on melee between orc factions he orchestrates the cutting of his own bonds and working to plan ahead. He knows his dive away from his captors is unlikely to succeed, but it does allow him to leave a marker of his presence, knowing that the larger and heavier orcs will obliterate any sign of his own passing. The Ring and Gollum baiting of Grishnakh was inspired, if incredibly risky. There's more to Pippin than "fool of a Took!"
Our order of operations between the book and the film has shifted a little. Jackson gives us this chapter before the pursuit of Aragorn, Legolas, and Gimli, committing to following chronology rather than the order of the chapters. This gives us a slightly more jumbled story at times, but also keeps the elements a pace and has the potential for a smoother and more integrated storyline. In this context however, it makes me more aware of the added content.
So it is, we know what happened with Merry and Pippin before their friends do.
Their captivity is streamlined, fewer interactions and opportunities to act out. Pippin never has the chance to dash off and drop his cloak pin, the hobbits carried and bound hand and foot. Instead he uses his teeth to pull it free and drop it, giving the only evidence of their continued presence. Their actual escape is shown through Aragorn's souped up Ranger Senses... or at least through appropriate flashbacks to the audience of what he's tracking.