I run Slackware -Current and last night was too lazy to lean over and press the power button my computer so I just opened the terminal and typed shutdown now. I forgot that this doesn't actually shut it down and the computer just sits on the login screen (tty no GUI login manager I start my DE with startx). I saw it this morning and for some reason after the login prompt and a ton of lines under it were filled with invalid packets iptables caught. Some originated from my gateway while others were from companies such as Akamai Technologies destined for that specific computer. I've never seen this happen before does anyone know what could have happened? Is it just a weird bug or possibly something malicious?

does your system have public (internet) IP? if yes, probably just a background noise. wait till you start your webserver, that's when you'll have lots of similar log messages to waste time looking at!
as for why, it's because your tty1 is probably also your main console where system prints kernel messages out(ones that usuallly appear in dmesg's output).