This came to mind after I misidentified a sim in the funny screenshots thread - I said Herb Oldie when I meant Herbert Goodie. The Oldies and the Goodies are so similar I'm constantly mixing them up. So, what Sims do you guys get mixed up?

For me (aside from the one I just mentioned)
- I used to get the two Caliente twins mixed up. Not so much anymore. It helps to change around their hairstyles to be not identical.
- Not exactly the same, but I keep thinking that Alexandra Teatherton is from Desiderata Valley for some reason, rather than Riverblossom Hills.

same-neighborhood characters with same first name at times get me confused if any of them appear in computer chat's menu.

Mercutio Monty and Ravi Bertino. Ravi is the Tricou kid who looks like Mercutio; I think he's called Patrick Teens in the game files. I really can't tell them apart on appearance. Especially if it's at the swimming pool and they're not wearing their regular outfits. Or I might tell them apart by behaviour -- Ravi is much nicer!

Oddly enough in my Veronaville it's Ravi who's the more significant character. He's self-effacing, promiscuous and kind-hearted. Mercutio has up till now largely stayed in the background with no love interest.

In my uberhood I often think I see John Burb on a community lot just to discover that he's actually Timothy Riley once I hover over him with the mouse. I think one of them needs a makeover.

All of them - I don't play the pre-mades. I have no idea who they are.

Nina and Dina Caliente. I can tell the sims apart - I just have trouble remembering which sim goes with which name because the names are so similar. I have been known to accidentally call one or the other of them "Tina" repeatedly. Usually I just refer to them as "Red" and "Blondie" - that way I know who I mean.

When I was new to playing Desiderata I had the Contrary and the Jocque live together, but constantly forgot who was married to whom - with tragic results. After directing the wrong sims to kiss, everyone's temper broke and the same day Edward Contrary died in a kitchen fire.

I don't get them mixed up but names I have trouble pronouncing.

Is Circe (Beaker) "Sirse" or "Curse"?

And I know most people pronounce Pascal (Curious) "Pas-cal" but I prefer "Pascle"

As for other names I often forget them, even my own Sims...cuz I have too many .

According to Wikipedia's entry on Circe, modern pronounciation of the name is usually something like Sir-See. Classical Greek did not have a soft "C" and it would have been pronounced something more like "Kirkee".

I used to get Nina and Dina's names mixed up all the time

No as I don't play them but my sims often get mixed up especially when I gave them names like Johan and Jonah, Ariana and Ariane and so on...

Today I got two teenage townies mixed up, Konrad Platz and... eh... another guy.

Desdemona and Ariel Capp. Can never remember which is the older.

Put Zoe Zimmerman and Ophelia Nigmos side by side. See a difference? I can't!

Fortunately their personalities are different, so I can dress and do their hair differently. But when Ripp autonomously flirted with Zoe after he got engaged to Ophelia, I put it down to his getting confused by their similarity.

Like this in Greek maybe
https://www.youtube.com/watch?v=rXW5wFQDges