Tony Tony Chopper had heard something strange was going on in the ship. Apparently people were getting stuck until they got some help and he didn't know what to make out of it. Until he found himself stuck and heard GLaDOS's messsage.
Having never heard this AI before, he was freaked out. Strange but familiar seeming plant growing out of the ceiling? Invisible walls? Strange voice with a cryptic message coming from nowhere??? Maybe Stacy was haunted!
After a few minutes of freaking out, Chopper remembered seeing
an announcement on his omnicom. So he decided to
ask for help. Hopefully help would come. In the mean time, he changed into his yeti human form and took to trying to force his way out.