When Dennis and Frank are destroying Art Slone's home, Frank cuts the shower curtains waist-high so 'everyone can see his junk'. In real life Charlie Day and his friend in college decided to get revenge on some third-floor guys by cutting the shower curtains waist-high.
The frat that Dennis was a member of and that the gang ignites a rivalry with was named Delta Omega Lambda, which combines the Delta Pi, Omega Mu's, and Lambda Lambda Lambda fraternities/sororities from the movie Revenge of the Nerds.