Angela appears, but doesn't speak.
Hammer's driver's license lists his address as 280 Maple Street, Quahog, RI. This is an actual house as seen on Google Maps.
HTT is short for HyperText Transfer
When Hammer gets hit by a bus and Peter goes to help, he gives his phone to an onlooker and tells him to snap a picture with a Clarendon filter. This references one of the famous filters on Instagram.