So many options, so I'll name a few and trust you can figure it out.
Btw this is not rare or odd. it's quite common.
IP over DNS
IP over ICMP
Spoofing a MAC Address of an authenticated client.
SE'ing for a user/pass combo.
Some url trickery to bypass their proxy rules occasionally works..
Im sure theres more but im thethered to my phone at the farm, so Im making this brief.
Or just paying for it
loljk