Can MOSFET drain current be higher than rated if the drain-source voltage is below rating?
It's actually quite a bit more complicated. You must consider the current, the voltage, and the pulse width (how long the device is turned on for, being allowed to cool completely between pulses). This is specified in the "safe operating area" (SOA) chart in many MOSFET datasheets.

Here's the SOA chart for one version of the 2N7000:



This shows that the 0.2 A limit is only valid when \$V_{ds} &lt; 2\ {\rm V}\$. For DC applications with higher \$V_{ds}\$ you must de-rate the maximum current.

However, in a pulsed applications it can carry higher current for a brief period.

Note: I found 2 different 2N7000 datasheets on the On Semi website. One is probably for the version made by the division that was formerly Fairchild Semiconductor, and one for part that's been made by On Semi and Motorola all along. One of these datasheets has no SOA plot at all. If you want to rely on the SOA curve it would probably be a good idea to be sure you are sourcing your parts from the product line that the more complete datasheet applies to.