SEPTA consists of over 1400 vehicles, each of these buses/trolleys/trains may be specified the same on order but after a well in service, SEPTA decides to test new equipment on these units. The New equipment could be anywhere from new propulsion systems to a new designation signs. Although not all notible oddities can be placed on this page, they are mentioned in this thread.
In mid 2008, SEPTA aquired six Comet I trailers and three Cab cars from NJT for service increasements on all of the eight push and pull sets that run on SEPTA's Regional Rail line during peak hours. Because these cares were slated for retirement, the comet I's went through a mini overhaul. The interior was refurbished, the cars got new decals and were renumbered 2590-2595 trailer and 2460-2461 for the cabs. The extra cab car 5118 is being used as an spare parts car and does not see revenue service. The comets have an HEP setup different from SEPTA's locomotives. This is the reason why the AEM-7 locomotives are changed often on Comet I set. The comet cars feature a very unique look since they are the only pull and pull vehicles to sport the current fade scheme. Typically, the Comet I set can be seen laying over on track 0 at Fern Rock Regional Rail station and can be seen during peak hour on the R5's Great Valley Flyer run. As of March 9th 2010, this set of comet Vs will appear on the Pennypack or the Neshaminy limited.
Comet 1 cab car 2460 at Wayne Jct. leading the Pennypack Limited. Picture taken by TRANSIT_FREAK.
After many years in the shops, 666 came back into passenger service on Jan, 23, 2009. 666 became the first BSS train car to have an all silver (Naked) theme after the car was serverly tagged with graffitii. "Sources say that the car was so heavly tagged that removing the graffitii actually removed the orange trim", Brandon S. 666 also has broken digital MPH readers in both of the cabs on each end and retains different font fleet numbers in red on side A of the car. A week after 666 returned to service it got an orange stripe under the roof lining impersonating the appearance of an M4 car. 666 looks similar to the CW cars but if you look closely, you will see the differences. During the SEPTA Rail Roadeo of 2010 it was reported that the rest of BSS cars will have all thier orange trims removed and keep a scheme like 666, therefore it would be easier for crews to remove the graffiti from trespassers.
Also take a look at this page for more info on the Modified BSS scheme.
666 at the 2010 Rail Roadeo. Picture Taken by Tritransit Area.