Can I plug a surge protector into an extension cord?

I wouldn’t. It’s a fire risk because extension cords aren’t designed for the constant load of a surge protector plus multiple devices—they’re meant for temporary, single-device use. The surge protector can draw more current than the cord can handle, especially if the cord is long, thin, or coiled, causing heat buildup that starts fires. You also lose surge protection since the extension cord adds resistance, blocking the low-impedance path to ground. Instead, get a longer, properly-rated surge protector cord or move electronics closer to the wall.