With the laptop off, flip it over and locate the intake and exhaust slats. Exhaust is usually on the side of back. Get a "Can of air", the cans found at a Office Depot type store.. You can also use a regular compressor - like for "tyres", just back off from the exhaust and blow! The canned air is much safer.
dust and crap should come out.... Keep it off the pillow/blanket, it needs to breathe... Since you have cats, you have to clean the heat sink once and a while.