Step 1: Go, be serious, get the job.
Step 2: Be very efficient, not over-the top PETA-like, but enough where you fit in about medium. Suggest innovative and positive things. Gain their respect and trust.
Step 3: Create support group meetings for other “like-minded” PETA members at a place not your home (so that your facade is upheld as I assume you are like me and have plenty of things that are “animal hazardous” or whatever.
Step 4: Slowly begin to differ in some minor opinions from the mainstream PETA mindset.
Step 5: Stop having meetings
Step 6: Wait until you are approached by former “meeting” attendee’s and asked “what happened”, “when is the next meeting”.
Step 7: Cull out the ones who you have won over using step 6 and begin your meetings again with this new group. The meetings as before can just be fun stuff like ping-pong, ect. but you should ALWAYS have at least one somewhat weighty discussion wherein you differ more and more from mainstream “PETA” thoughts. You should be subtly undermining their minor points.
Step 8: After getting to know your new group of devotees better, inform them that you feel the need to quit working for PETA due to their belifes, which by now you should have them beliving that PETA is indeed “the bad guy” (in whatever way, doesn’t matter, as long as PETA is “the bad guy” somehow). Tell them that you cannot work for a place that supports/encourages insert PETA position that you and your group have deemed bad here. Remember, you are now respected and liked as well as valuable to your co-workers and the task you perform as well as I am assuming well-treated/payed ok. You quitting may indeed get them to quit or SERIOUSLY question PETA as well.
Step 9: After you have formed the friendships and they are solid (which, belive it or not you may actually create real friends from this) you should tell them subtly that you did the PETA thing on a dare, but once you got to know them, ect. you really liked them (by now you may like your “cabinet”, if not their beliefs) and you stayed on much longer after winning the bet but finally left because you felt “like a liar” and it was against your belifes. They will be angry, you will lose some of them, but in the end, at this point you have a STRONG chance of converting any that stay your friend to your TRUE beliefs. I.E. that beef/leather/whatever is cool, beating animals or hurting them for fun in diabolical ways is bad.
Of course, during your stay at PETA (you may be discovered and terminated at any time, keep in mind) you should subtly plant wrappers from burgerking ect. in co-workers trash-cans.
Tip people off to PETA rallys
Give out co-workers extension numbers and personal e-mail addresses, if not phone numbers.
Dissolve crushed ex-lax tablets in the coffee (TECHINICALLY illegal as it is considering administering medication without license or consent, but noone will bust you I bet).
Fart on the elevator when it is crowded whenever possible, but make sure noone hears it.
Spread false rumors or start them. ex. “Did you hear the janitor found a McDonalds wrapper in Cathy’s trash?” (knowing full-well you planted it).
Hide bits of easily concealed meat products such as sausage lings, ect. in co-workers drawers.
(After they catch on that someone is planting stuff, make sure to plant a bit in your cubicle as well).
Anywho, this should have you off to a good start and if you masterplan is side-railed or you are terminated, you still will have stuck many a small barb in their side even if you did not split their work force and steal converts.