RC remote controlled toys work relatively easy. They need to be cheap. The manufacturers keep costs as low as possible.
On the transmitter side a quarz chrystal is used to keep the transmitter on the defined frequency. In our case it is 27.415Mhz. The transmitter needs to maintain a stable frequency, that's why the quartz crystal is used ( http://en.wikipedia.org/wiki/Crystal_oscillator
On the receiver side no quartz crystal is used because it costs to much money. The stability of modern receiver circuits is good enough for a simple toy. To make the receiver work it needs to filter the radio frequencies to detect only the signal sent by the transmitter ( http://en.wikipedia.org/wiki/Receiver_(radio)
). There is at least one filter mounted on the input, near the antenna. While using superhet ( http://en.wikipedia.org/wiki/Superhet
) technology there is also a if band filter needed. Most of the time this is a small ceramic resonator.
Looking at the Wikipeda article you will find a picture under "Design and its evolution". The block named "RF Amplifier" is the place where the first filter, designed with a coil and a capacitor, sits. The second filter, the resonator, is marked with "Filter".
I added a "partly re engineered" schematic of the input filter. "Partly" means, that only the important components are drawn.