Shameless Is Full Of Age Blunders (& Fans Notice Them All)
Most TV shows have rules in place for aging characters. "The Simpsons" and many other animated shows tend to keep characters the same age even as the years around them change. Then something like "The Office" follows characters as they progress one year through the next. Then there's whatever "Shameless" was doing.
Audiences got to see characters, particularly the Gallagher children, age progressively from one season to the next, but many have pointed out the inconsistency between such ages. Take Fiona (Emmy Rossum), for instance. Redditor u/SATX-Batman kicked off a ton of discourse, writing, "Why did they age Fiona down? In season 1 they mention she is 25 but in S4E12 she says she is 23, I also vaguely remember someone saying she is almost 30 in a previous season." Plenty of people chime in with their own timelines, but assuming each season lasts roughly a year, it just doesn't add up, and things only get more confusing when taking into account the other kids.
No one can figure out the Gallaghers' ages
Ultimately, it seems as though characters' ages vary depending on the needs of the plot. Frank's (William H. Macy) age doesn't necessarily matter because he's a full-grown adult the whole way through. But when looking at the Gallagher children, some of whom go from high school to adult with jobs, it gets a little messy.
It gets especially tricky when considering Lip (Jeremy Allen White) and Ian (Cameron Monaghan), who are supposed to only be one year apart in age. But they seem to age at different rates, as u/Le_re11 points out, "I was sat thinking about Ian's age. He's 15 in season 1 and 17 in season 5. Yet in season 7 he's presumably 21 since Lip is said to be 22 and there's also the whole ID thing with the bar with Trevor. Ian literally ages 2 years in 5 seasons and then 4 years in two seasons."
There's also confusion surrounding Debbie (Emma Kenney) and Carl (Ethan Cutkosky). Earlier in the series, it's established that Debbie's a little older than Carl, but as u/Kingz-Ghostt points out, "I'm on season 7 episode 2 and they say Carl is 16, though last season they said Debbie was 15." Everyone tells the Redditor not to pay attention to ages because it never adds up. Liam (Christian Isaiah) also had a drastic age change, as u/project_built mentions, "Liam went from 4 to 9 in between seasons so i wouldn't look too far into age consistency." Some explanations have emerged, with some people stating how not every single correlates to a single year, but even that idea comes with problems. Upon rewatching the series, it'd be best not to think about it too hard.