Toward the end of the series, Tom is established to have been born in 1985 and thus is in his mid-to-late 20s throughout the series. He and Wendy are also established to be close to the same age, as he tells Ron they "met in college." However, in Season 2, which takes place in 2009, Wendy is already practicing as a surgeon. If she is around the age of 24-25, it would be highly unlikely that she is fully practicing as a surgeon at that point.
When Leslie shows up drunk at Dave's house, Amy Poehler can be seen breaking character as she struggles to hold back laughter. Furthermore, Louis C.K. can noticeably be seen smiling in response to Leslie's high five. It is highly unlikely that Dave would smile in this situation due to the reverent nature of the character, thus it most likely being a breech of character on Louis C.K's part.