Rod Flanders wears the number 6, and his brother Todd wears the number 66. When Bart is named the starting quarterback, Rod and Todd stand next to each other, their numbers form 666, the sign of the beast.
The hat Homer is wearing is one of the many Easter eggs in the series. He purchased it in Season 8, and it makes three more appearances in the series to date. Only one of those is it in Tom Landry's possesion.