If the player is somewhat stealthy and is pretty good at stealing things, he can try to steal the radio signal jammer for Bear's C4 heart bomb. Kyle has the radio trigger on a secret item on his person. The player will have to figure out that the item in question is Kyle's gaudy watch which has never worked in telling time (first clue). The player can then try to steal Kyle's watch while he sleeps, which would take quite a bit of high sneaking ability. However, the player could try to get Kyle very drunk and then try to steal the watch after he passes out, thus lowering the risk of getting caught considerably. Either way, when the player has control of the trigger, it's up to him if he wants to free Bear from the device, or take control of Bear.
Character type completion breakdown
Combat Boy – Pretty much anyone can talk Kyle into getting drunk, especially if the PC brings quite a bit of booze. This will increase any class type's chances of stealing Kyle's watch trigger.
Diplomacy Boy – Diplomacy Boy will have an easier time figuring out what controls Bear by talking to Kyle. Getting Kyle drunk makes Kyle talk too much, which will reveal his secret.
Science Boy – Science Boy would have a pretty good chance of figuring out that Kyle's watch is being used for something other than telling time. At that discovery, Science Boy can go the drunk/pass out route to get the watch.
Stealth Boy – Once the player figures out what's what, he should have no trouble sneaking up on a sleeping Kyle and stealing the watch.