We call them by the three letters of their plate numbers..
Previous cars:
NPY - Nappy
PTP - PTP
PMC - PMC
PEA- PEA
PEN - PEN
UMR - UMR
lately, we called them Lance (for Lancer), Lynxie (for Lynx)
hehe kami rin. our toddler nephew calls our vehicles also by its plate number's first 3 letters, kaya yun nakasanayan na... sila TNY, TTT, UTL, UDA and XBH.