[scott_s]

Not the same kind, though the difference was subtle, and maybe not an important distinction to most people. In ICQ, you sent discrete messages back and forth. You could (I believe) look at the last message while replying, but you didn't have a chat history integrated into the same window where you replied. I used both ICQ and AIM in the '90s and early 2000s, even talking to the same people, and the interactions felt very different. ICQ felt like it was between email and AIM in the communication spectrum: obviously interactive and real-time, but each person tended to say more in each message. AIM's style encouraged more call-response conversations.

I point this out because I think it's an interesting case of user-interface design influencing use, even though on the surface they're both "chat apps."

[52-6F-62]

I still have my ICQ number burned into my brain. There are other, more important, numbers I should be remembering and at times cannot, but that ICQ number is there.

[adamcharnock]

Tangent for UK people: I have the emergency services number from The IT Crowd burned into my brain too: 01189998819991197253

WHY?!

[huxley]

Well, that's easy to remember!

[sixstringtheory]

US person here, singing the song in my head as I read your comment :)

[52-6F-62]

There it is—my yearly reminder to rewatch that show. Cheers.

[nasredin]

I was quite proud of my 7-digit (in ICQ world, the SMALLER the UIN (why do I still remember these acronyms!) the BIGGER your penis was) ICQ number that started with 404.

404. Quite clever, eh? I guess there was a lot more HTTP 404 errors back then.

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Yes, I too remember my ICQ number but not the birthdays of... I PLEAD THE FIFTH YOUR HONOR!

[emidln]

I do too, but I have no idea what my password is.

[digi_owl]

I seem to recall that the ICQ window had a multiple modes.

One of them was individual messages, but another allowed each party to see what the other was typing in real time.

Also, if one want to talk about chat histories one should not forget about IRC.

[nasredin]

Hmmm.

I thought they were both instant messengers, just AIM was more popular in US and ICQ was more popular in Israel and Eastern Europe.

One distinct feature AIM had were the IRC-like chat rooms.

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You may be confused WRT an ICQ "offline messaging" feature, which IIRC allowed one to send messages to offline contacts, who would see the message when they signed in.

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Also in case you didn't know: ICQ is a (too lazy) of "I Seek You".

[scott_s]

They were both "instant messengers." But their interface was different enough to lead to different behavior.